refactoring the build.gradle file to be clearer

The build script included all kind of utilities logic, which I want to use
in other places too (separate git?), I've moved that away

Change-Id: Ie550296d029216db6e4b9fb99745815103408be3
refactored Change-Log fragment for using BuildConfig

BuildConfig is a static constant method to obtain build time data.
ChangeLog fragment will use that to display the version name.
The BuildConfig will also be used to ensure correct formatting
of the version name.

Change-Id: Icbf376d8427d18d2ebac236cc159eff1bde56439