Announce selected port better.

- Use actually used port in the printed message.
- Flush the printed message to make sure it ends to the sys.stdout.
- Support writing port number to a given `port_file`.

Implements code changes related to issue #3. Documentation missing.
Test system clean-up.

Got rid of separate servercontroller.py that was used by run.py in favor
of starting the remote library/server using Process library in by every
test suite. This eases using different libraries by different suites in
the future.