[java-templates] Transactional Java API

Transform Kurento Client remote objects from interfaces to classes
Refactor 'new MediaElement.Builder(...)' by 'MediaElement.with(...)'
Refactor 'client.createMediaPipeline()' by
'MediaPipeline.with(client).create()'
Refactor fusioning RomClient with RomFactory in RomManager
Refactor reducing extra RomManager param in RemoteObject
Remove MediaPipeline auto-generation and minor improvs
Initial complete prototype of transaction support in kurento-client
Add compatibility with Kurento 5.0.3 deprecating classes and methods
Reduce visibility of some methods in Transaction class
Remove async methods and other improvements
Refactor AbstractMediaObject by KurentoObject and remove continuations

Change-Id: I6cd0fd12f097e232d074e1a882ea62f414a5aca6