Improve javadoc instructions in CONTRIBUTING

Add a new step of removing old javadoc files from build/ folder, since the
javadoc gradle task seems to keep the old files around.
Rename Prototype to Repository.

Upgrade strong-remoting-android dependency version to 1.1.0-SNAPSHOT

Bump up the version number to 1.1.0
Update AndroidStudio project files.

Remove .idea/libraries/ from version control as they are auto-generated
and frequently updated.
Update API javadoc.