Change Maven groupID to com.google.gerrit

This allows us to publish gwtorm on Maven central in the same project
with Gerrit.

Change-Id: I5f632fa5c77a3702900cf82835836b6d7241d8b4
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

pom.xml

diff --git a/pom.xml b/pom.xml
index d5b3bd8..4041475 100644
--- a/pom.xml
+++ b/pom.xml
@@ -18,7 +18,7 @@
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
   <modelVersion>4.0.0</modelVersion>
-  <groupId>gwtorm</groupId>
+  <groupId>com.google.gerrit</groupId>
   <artifactId>gwtorm</artifactId>
   <packaging>jar</packaging>
   <version>1.12-SNAPSHOT</version>