Several changes. See extended description.

Changes:
- Bit fields, dec/hex rows changed from Buttons to TextViews
- Background colors of the game fields are changed
- Small changes at the game logic.
Bugfixes:
- The hex keyboard layout wasn't fully visible all the time on handset
devices. This got fixed by adding another hex layout which gets selected
on handset devices.
- A crash of the application on handset devices if the Start Button was
pressed in one situation.
- The mActiveRows gets resettet now when a new level is reached