Commit included ATMegaCard changes not meant for production.

This reverts commit a30c7068.

CardReader: Change standby message.

The buffer that was used to calculate it did not contain the current salt.
Instead of creating a new buffer, we now use the sha1 block functions directly
and hash key and salt in two calls.

Additionally a ctx2hashhead function is added to convert only the first 4 bytes
of the hash instead of converting all 20 bytes and throwing 16 bytes away afterwards.

Display control error messages on Cardreader display
Reset Cardreader display after 4 seconds of idle to make sure the display is clean
when a new user inserts a card.
Detect a dead portal control and display an error message.

CardReader, Control: Change Polarity of Card-Detection / Reader-Power-Request pin to match the final hardware.

CardReader: Reduce APDU timeout to 600ms for the first answer byte and 300ms for the following bytes

Control: Add support for card key initialization/clearing
Control: Make debug output depend on #defines

Control: Wait for Cardreader LCD commands to be acked.
Control: Refactor state constant names.

reader power completely).
CardReader: Send reply when an LCD command is complete.

commin/i2c: Support bitrate changes (this seems to be broken, needs debugging)