Reorganize src/client: Closes bug #713873

This is purely code file deletion and moving with those changes
reflected in CMakeLists.txt.  The .gitignore change should've
happened some time back when we removed the DBus server app.

This change is to make the client source code a bit more logical
and hopefully make it easy for contributors to drill down and find
the module they want to work on.

In addition, unused client code was deleted.  src/common was intended
to be code common to the various apps built here, but since that never
panned out, it was moved into the client base.