[shill] Start cleaning up some of the naming confusion

We have, so far, not been tidy wrt our objects naming themselves,
for human-readable stuff, RPC-path stuff, etc.

This starts to clean up some of that confusion.

BUG=chromium-os:17744
TEST=unit tests

Change-Id: If4d7f61ba51e527984328a0ccdf4dec461b36074
Reviewed-on: http://gerrit.chromium.org/gerrit/4311
Reviewed-by: Chris Masone <cmasone@chromium.org>
Tested-by: Chris Masone <cmasone@chromium.org>