update AGP to fix error on CI-build

Merge branch 'hotfix/0.7.1'

do some refactoring on MediaRepository to get a second comit because …

…of the way our versionCode is calculated

update android-gradle-plugin and ktlint-gradle-plugin

update version and fix package names and imports for initializers

update Version because i forgot for the last hotfix

add cause to snackbar

fix some warnings

reset versionfile to 0.5.2

formatting (ktlint)