provide the official ros maven repo as a fallback

Even when no ROS_MAVEN_REPOSITORY variable is set (windows). This also
lets the user provide their own repo via the variable that will get searched
before the official one would. This refs #46.

Author: stonier

gradle_plugins/src/main/groovy/org/ros/gradle_plugins/RosPlugin.groovy

@@ -41,6 +41,13 @@ class RosPlugin implements Plugin<Project> {
           url project.ros.mavenRepository
         }
       }
+      /* 
+       * This will often be the same as ROS_MAVEN_REPOSITORY, but this way it lets a user
+       * provide a repository of their own via the environment variable and use this as a fallback.
+       */
+      maven {
+        url "https://github.com/rosjava/rosjava_mvn_repo/raw/master"
+      }
       mavenLocal()
       maven {
         url "http://repository.springsource.com/maven/bundles/release"
@@ -62,6 +69,6 @@ class RosPluginExtension {
   RosPluginExtension() {
     /* Initialising the strings here gets rid of the dynamic property deprecated warnings. */
     this.mavenDeploymentRepository = ""
-    this.mavenRepository = "https://github.com/rosjava/rosjava_mvn_repo/raw/master"
+    this.mavenRepository = ""
   }
 }