relative filepath handling

[cefect]

Continuation of fix for issue #104

implemented relative pathing for all unit tests. All tests are passing. The following is still needed:

• Go through and check that wherever a build tool writes a filepath to the control file, the absolute_fp flag is respected (e.g., here).
• extend test_tutorial_02.test_tutorial_02a() to include `absolute_fp. Should look something like:

@pytest.mark.parametrize('absolute_fp',[True, False])

Note that the absolute_fp attribute on the BuildDialog is properly setting its state based on the UI radio button, and this variable is also being collected with inherit_fieldNames (then presumably being passed to the worker inits as **kwargs). See here for example.