* luks_device: add support for keyslots
* luks_device: replace python3 format strings with python2 format strings, remove print statements
* luks_device: add missing copyright information in keyslot integration test files
* luks_device: updated failing unit tests for keyslot support
* luks_device: improve detection of luks version
* luks_device: Update documentation on keyslot parameters, minor code improvements
* luks_device: improve validation of keyslot parameters, fix tests for systems that do not support luks2
* luks_device: correct spelling and errors in documentation and output, check all possible locations for LUKS2 header