Merge pull request #34 from ironjan/develop

Hopefully fixed random db crashes on some Android versions.
Update gradle version
Add image previews for menus
Build script improvements

 * Moved buildscript dependencies to main build file
 * Increased android gradle tools version
Increased app version
Merge branch 'cbruegg-master' into pr36

Conflicts:
	app/build.gradle
	build.gradle
	gradle/wrapper/gradle-wrapper.properties
Deleted unused resource file
Reordered entries and added ScrollView
Added developer list to about
Fixed ion version, removed method breaking travis build
Merge pull request #37 from ironjan/pr36

Merged #36 with some additional changes