Create and edit category

See merge request !14

# Conflicts:
#   app/src/main/java/cz/muni/sutralog/ui/list/CategoryListFragment.kt
#   app/src/main/java/cz/muni/sutralog/ui/list/RockListFragment.kt

Rock filtering

See merge request !13

# Conflicts:
#	app/src/main/java/cz/muni/sutralog/data/RockPresentableListItem.kt
#	app/src/main/java/cz/muni/sutralog/ui/list/RockListFragment.kt