Remove dependency on kobo.

This patch moves a lot of code from kobo to Beaker.
Some unused code has already not been transferred over, but further
efforts should be made at some point to remove unecessary code
that has been transferred over. Also some code that came from multiple
modules in kobo has been crammed into one (bkr.client.command for example).

Change-Id: I7436d630152d6dcec10ebeb8e90a94f5a9581057