Added tagid output and argument subparsers

Switching between swid output and tagid output
happens via subcommands swid and tagid (tnc-ba/strongTNC#63)
Corrected over idented lines
Removed unused directory
Moved software_id generator to separate file
Renamed tagid to software-id
Updated help strings
Updated help/usage strings
Update README.rst
Moved generators to separate package