[git] create gen folder for generated sources in git4idea module and move Git4ideaIcons

This fixes icon for Deep Compare action (since Git4ideaIcons was located in resources folder it was not compiled).

plugins/git4idea/gen/icons/Git4ideaIcons.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2013 JetBrains s.r.o.
+ * Copyright 2000-2016 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

plugins/git4idea/git4idea.iml

@@ -9,6 +9,7 @@
       <sourceFolder url="file://$MODULE_DIR$/test-features" isTestSource="true" />
       <sourceFolder url="file://$MODULE_DIR$/test-stepdefs" isTestSource="true" />
       <sourceFolder url="file://$MODULE_DIR$/resources" type="java-resource" />
+      <sourceFolder url="file://$MODULE_DIR$/gen" isTestSource="false" generated="true" />
     </content>
     <orderEntry type="inheritedJdk" />
     <orderEntry type="sourceFolder" forTests="false" />