…#125)

- in some activities the code for setting the locale was missing and therefore a simple turn of the device switched to localized texts even if localized resources were disabled
- for all other activities there was the problem that the locale was set only in onCreate but in some special cases the config is reset but only onResume gets called (e.g. when turning the device, hitting the home button, turning the device back and then switching to AT again). Setting it only in onResume would be too late for the regular cases. The code is almost a noop if there is no change to be done so it seems ok to call it twice.
- created two baseclasses for activities to encapsulate the logic and increase the chance that a new activity will be based on that classes and the code will not be forgotten
- might fix issue Zukero#125 "Localized resources showing even when disabled"
- ways of working solutions for setting the locale differ from API level to API level (see https://proandroiddev.com/change-language-programmatically-at-runtime-on-android-5e6bc15c758)
- tested on android Pie and Marshmallow

…oblems on some activities where still the localized content was shown