[ONOS-4797] Implement the Driver for handling Arista switch

Arista switch with its recent network OS, EOS, supports remote configuration & control. The protocol for this is Arista's proprietary but REST style.
Since ONOS has already REST southbound protocol, the control of Arista switch can be easily done by using this.

- Implemnted driver Loader for Arista switch
- Implemented DeviceDescriptionDiscovery for Arista switch
- [Deleted] Implemented the method sending post to Arista switch and return the result as a String

Change-Id: I9d4b8f0d707361949ff530ff414adb0437ae87d9
diff --git a/drivers/arista/src/main/resources/arista-drivers.xml b/drivers/arista/src/main/resources/arista-drivers.xml
new file mode 100755
index 0000000..c007040
--- /dev/null
+++ b/drivers/arista/src/main/resources/arista-drivers.xml
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ Copyright 2016 Open Networking Laboratory
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~     http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+<drivers>
+    <driver name="restArista" manufacturer="Arista Networks" hwVersion="1.0.0" swVersion="1.0.0">
+        <behaviour api="org.onosproject.net.device.DeviceDescriptionDiscovery"
+                   impl="org.onosproject.drivers.arista.DeviceDescriptionDiscoveryAristaImpl"/>
+    </driver>
+</drivers>
+