Adding and fixing javados.

Change-Id: I38eddb0b11630cdd83c5d1e5d5dc393ee2555897
diff --git a/docs/external.xml b/docs/external.xml
index c730c90..30c3f9c 100644
--- a/docs/external.xml
+++ b/docs/external.xml
@@ -49,7 +49,7 @@
                 <version>2.10.1</version>
                 <configuration>
                     <show>package</show>
-                    <excludePackageNames>org.onlab.thirdparty:*.impl:*.impl.*:org.onosproject.provider.*:org.onosproject.gui:org.onosproject.rest:org.onosproject.cli*:org.onosproject.tvue:org.onosproject.foo:org.onosproject.mobility:org.onosproject.proxyarp:org.onosproject.fwd:org.onosproject.ifwd:org.onosproject.optical:org.onosproject.config:org.onosproject.calendar:org.onosproject.sdnip*:org.onosproject.oecfg:org.onosproject.metrics:org.onosproject.store.*:org.onosproject.openflow.*:org.onosproject.common.*</excludePackageNames>
+                    <excludePackageNames>org.onlab.thirdparty:*.impl:*.impl.*:org.onosproject.provider.*:org.onosproject.gui:org.onosproject.rest:org.onosproject.cli*:org.onosproject.tvue:org.onosproject.foo:org.onosproject.mobility:org.onosproject.proxyarp:org.onosproject.fwd:org.onosproject.ifwd:org.onosproject.optical:org.onosproject.config:org.onosproject.calendar:org.onosproject.sdnip*:org.onosproject.oecfg:org.onosproject.metrics:org.onosproject.store.*:org.onosproject.openflow.*:org.onosproject.common.*:org.onosproject.net.group.impl</excludePackageNames>
                     <docfilessubdirs>true</docfilessubdirs>
                     <doctitle>ONOS Java API</doctitle>
                     <groups>
diff --git a/docs/pom.xml b/docs/pom.xml
index 3a1bfb9..eec3b1e 100644
--- a/docs/pom.xml
+++ b/docs/pom.xml
@@ -61,7 +61,7 @@
                         <group>
                             <title>Core Subsystems</title>
                             <packages>
-                                org.onosproject.impl:org.onosproject.core.impl:org.onosproject.cluster.impl:org.onosproject.net.device.impl:org.onosproject.net.link.impl:org.onosproject.net.host.impl:org.onosproject.net.topology.impl:org.onosproject.net.packet.impl:org.onosproject.net.flow.impl:org.onosproject.net.*.impl:org.onosproject.event.impl:org.onosproject.net.intent.impl:org.onosproject.net.proxyarp.impl:org.onosproject.mastership.impl:org.onosproject.net.resource.impl:org.onosproject.json:org.onosproject.json.*:org.onosproject.provider.host.impl:org.onosproject.provider.lldp.impl:org.onosproject.net.statistic.impl:org.onosproject.app.impl:org.onosproject.common.*
+                                org.onosproject.impl:org.onosproject.core.impl:org.onosproject.cluster.impl:org.onosproject.net.device.impl:org.onosproject.net.link.impl:org.onosproject.net.host.impl:org.onosproject.net.topology.impl:org.onosproject.net.packet.impl:org.onosproject.net.flow.impl:org.onosproject.net.*.impl:org.onosproject.event.impl:org.onosproject.net.intent.impl:org.onosproject.net.proxyarp.impl:org.onosproject.mastership.impl:org.onosproject.net.resource.impl:org.onosproject.json:org.onosproject.json.*:org.onosproject.provider.host.impl:org.onosproject.provider.lldp.impl:org.onosproject.net.statistic.impl:org.onosproject.app.impl:org.onosproject.common.*:org.onosproject.net.group.impl
                             </packages>
                         </group>
                         <group>
@@ -78,6 +78,13 @@
                             </packages>
                         </group>
                         <group>
+                            <title>Null Providers
+                            </title>
+                            <packages>
+                                org.onosproject.provider.nil.*
+                            </packages>
+                        </group>
+                        <group>
                             <title>Utilities</title>
                             <packages>
                                 org.onlab.*
diff --git a/docs/src/main/javadoc/doc-files/onos-subsystems.png b/docs/src/main/javadoc/doc-files/onos-subsystems.png
new file mode 100644
index 0000000..a6100c5
--- /dev/null
+++ b/docs/src/main/javadoc/doc-files/onos-subsystems.png
Binary files differ
diff --git a/docs/src/main/javadoc/overview.html b/docs/src/main/javadoc/overview.html
index a3e32d9..d3712ab 100644
--- a/docs/src/main/javadoc/overview.html
+++ b/docs/src/main/javadoc/overview.html
@@ -39,7 +39,15 @@
 </p>
 
 <p>
-    The following diagram describes a general structure of each ONOS subsystem:
+    The figure below provides a visual inventory of the various ONOS subsystems.
+    The ones with the gray outline represent either work in progress features
+    planned for release in 2015.<br>
+    <img src="doc-files/onos-subsystems.png" alt="ONOS architecture tiers">
+
+</p>
+
+<p>
+    The following diagram describes the general structure of each ONOS subsystem:
     <br>
     <img src="doc-files/onos-subsystem.png" alt="ONOS subsystem structure"><br>
     For example, the device-subsystem comprises of a core