preparing version 1.5
Merge branch 'hotfix/1.4.1_update_services_lib' into develop

Conflicts:
	android-maps-extensions-demo/pom.xml
	android-maps-extensions-libs-installer/pom.xml
	android-maps-extensions/AndroidManifest.xml
	android-maps-extensions/pom.xml
	google-play-services-samples/pom.xml
	pom.xml
fixed warnings
updated gitignore
interface for changing cluster group
demo example using Marker.setClusterGroup
forwarding cluster group change event to ClusteringStrategy
implemented cluster groups (issues 10, 19, 22)
upst
replaced IconDataProvider with ClusterOptionsProvider
modified DemoIconProvider to implement ClusterOptionsProvider
cluster groups demo using getClusterGroup
updated version to 1.5, demo version 1.2
Merge branch 'release/1.5_cluster_groups'