Bump pom.xml to Gerrit-2.8.1, added plugin repository

Bump the pom.xml version to 2.8.1 to match released version of Gerrit.
Added https://gerrit-api.commondatastorage.googleapis.com/release
to repositories section to ensure latest plugin API is available.

Change-Id: I7a5d7533a6ffadb2ff28ede1cdf4fc61c0b1cff7

pom.xml

diff --git a/pom.xml b/pom.xml
index 2105bfb..7ca36c9 100644
--- a/pom.xml
+++ b/pom.xml
@@ -20,7 +20,7 @@
   <artifactId>gitblit-plugin</artifactId>
   <description>GitBlit for Gerrit integrated as a plugin</description>
   <name>Gerrit - GitBlit Plugin</name>
-  <version>2.8-SNAPSHOT</version>
+  <version>2.8.1</version>
   <properties>
     <Gerrit-ApiType>plugin</Gerrit-ApiType>
     <Gerrit-ApiVersion>${project.version}</Gerrit-ApiVersion>
@@ -195,6 +195,10 @@
 
   <repositories>
     <repository>
+      <id>gerrit-api-repository</id>
+      <url>https://gerrit-api.commondatastorage.googleapis.com/release</url>
+    </repository>
+    <repository>
       <id>gerritforge-gitblit-repository</id>
       <url>http://gerritforge.com/snapshot/</url>
     </repository>