Use this to set the available UART ports and default timer values.
The latter gets rid of FIJI::DEFAULT_TIMER_VALUE by replacing it with
FIJI::Settings::default_timer_value().

However, it requires some non-trivial changes, namely the refactoring
of FIJI::Tests. While at it, we got almost rid of the 'ext' field in
Tests. It is lessened to 'TESTPATMAP' containing info to verify tests.

The refactoring also allows for unification of opening of tests files
in the EE GUI. To that end this patch adds _read_tests_file() that
handles creation of the Tests instance and handle user interaction if
need be.