gkeys/base.py: Improve help layout, unify no action help with py2.7
gkeys/base.py: Shorten and enhance epilog message

The message was hitting a forced line wrapping right at "system"
Enhance (capitolize) a few important words.
gkeys: Separate and sort the avaialbe actions into groups

Create false actions for the 3 groups to help improve the argparse help output.
These stubb functions can be used later to organize and print the group specific actions only.
gkeys/base.py: Add a justdoit option, fix boolean options
Map sub commands to class functions

This allows the use of hypens in subcommands because 
they are no longer directly mapped to the class function they initiate.
Do some more fine tuning of the grouping identifiers.
gkeyldap/cli.py: Remove unused imports