XMPP as SBI support: implementation of core XMPP and Xmpp Device Provider

State machine handled by XmppSession interface, most of tests implemented

XmppDeviceFactory re-designed, tests updated

pom and BUCK files updated

Change-Id: I4c6955e091169c945415084cbb000c61b474c0fc
diff --git a/providers/xmpp/pom.xml b/providers/xmpp/pom.xml
new file mode 100644
index 0000000..3ce40d1
--- /dev/null
+++ b/providers/xmpp/pom.xml
@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>onos-providers</artifactId>
+        <groupId>org.onosproject</groupId>
+        <version>1.13.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>onos-xmpp-providers</artifactId>
+
+    <modules>
+        <module>onos-xmpp-provider-device</module>
+    </modules>
+
+</project>
\ No newline at end of file