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.

These tests replicate the first four functional tests cases in the SIM sub-section of the ofono test plan:

https://wiki.ubuntu.com/Process/Merges/TestPlans/ofono/SIM

These scripts are self-documenting.  Use pydoc, or read the source directly.  Once we build more tests, this internal documentation can be converted to HTML and linked to the wiki for reference.

"ServiceNumbers" property is not on the list. This caused the test to fail with my SIMs.