Initial gradle support

* compiling works
* instrumentTest currently only uses the catroidTest module
Libgdx native extensions are now included & Android Studio import works
Merged catroidUiTest project into catroidTest
Moved gdx native jar because eclipse doesn't like it
Added sdk version to gradle
removed catroidUiTest from source tests
rewrite changelog to markdown
Merge pull request #818 from Catrobat/rewriteChangelogToMd

Rewrite changelog to Markdown
catroidSourceTest now builds with gradle
Added Polidea TestRunner
Using older version of build tools until jenkins is updated
Changed namespace for BrickLayout view to res-auto
Added jenkins task for package renaming to build.gradle
Merge pull request #819 from Catrobat/xml_namespace_refactor

Changed namespace for BrickLayout view to res-auto
Merge branch 'master' into gradle

Conflicts:
	catroidUiTest/AndroidManifest.xml
Added build code parameter support to build.gradle
Now setting the package name in build.gradle so it doesn't get messed up when renaming package
Added git describe to build config
fixes the PointToBrickTest
Merge pull request #820 from Catrobat/fixTestcasePointToBrick

fixes the PointToBrickTest