adding Gradle wrapper.

As suggested in http://www.gradle.org/docs/current/userguide/gradle_wrapper.html the Gradle Wrapper is the preferred way of starting a Gradle build. The wrapper is something should check into version control.
adding Grunt and Bower task to Gradle
updating requirements and build documentation
renaming note.md to README.md
adding global README.
better handling metadata defaults model values
better handling object model defaults values
better handling screen model defaults values
bug fix. addresses #54
bug fix. addresses #54
improve robustness when checking version
remove useless log and replace log by debug
catch and log exception in case of error
create background model
useless commit - dahuapp.js
indent generated .dahu file properly
create specific object models depending on its type
create background view
create background template
output generated screencast model on debug logger