Added sendkeys command to vbox provider.
Cleaned up internal logging

* VEEWEE_LOG environment variable now specifies the loglevel
* debug option sets VEEWEE_LOG to "DEBUG"
Added VT1 - VT12 key code specials for VT switching.
Moved scancode map generation to class level.
Merge pull request #560 from Drachenfels-GmbH/master

internal logging & vbox sendkeys command