The biggest update to date.

* Login prompt on first launch (#11)
* Merge multiple pages into one (#14)
* New, fresh cards layout
* New Untis parser, supporting many more Untis systems than before
* Automatic detection of Untis systems
* Parsing support on older Android versions
* Strikethrough support
* Dark and black theme
* Long press to share entry
* Zoom in on images
* Display more useful labels on page selector
* Invert image colors support
* Blue-colored splash screen
* Localized update notifications
* Automatically switch to correct encoding
* Google Play flavor
