Fix keyboard issues

[jasger9000]

Hello to all,

This PR aims to fix three things:

1. The keyboard handling for clocking and typing
2. Removing the duplicated code from the different modes into one file
3. Making it impossible to input non-valid characters

Closes #36.

This should make it a lot easier to maintain the project (since you don't have to duplicate so much) and decrease its size.
It also is in direct conflict with #34 since we solve the same problem.