mel list: support '__micro__' dir
mel list: support '__micro__' dir

Now that there is a special sub-directory for microscope images, support
it in the 'mel list' command.

This prevents ignoring real moles with '__micro__' subdirs and prevents
mis-recognising '__micro__' subdirs as moles.

Test Plan:

Ran in mole hierarchy and verify expected output
    $ mel list

aevri/mel,aevri/mel