test/rilmodem: add new SIM functional tests

This commit adds Python unittest-based functional test scripts
used to test the SIM functionality of an instance of ofono using
the rilmodem/mtkmodem drivers.
test-sims-online: document cmd-line args
test/rilmodem: add test-sim-removal
Merge pull request #136 from tonyespy/first-sim-tests

Tested in mako and krillin, vivid.