Breaking up the importer's huge icommon.py file

[vila]

>>>>> Max Bowsher <_ at maxb.eu> writes:

<snip/>

    > SubprocessMonitor and ThreadDriver look fairly generic - the only
    > reasons I wanted to merge them in was to spare me having to come
    > up with a good name for a separate file to put them, and it
    > doesn't seem likely that they'll need to be re-used outside
    > mass_import.py

My main reason to keep them *outside* of mass_import.py was to ensure I
wasn't accidentally mixing the features provided there with the specific
needs of mass_import (from memory, mainly db access and logging).

I won't mind an ithreads.py module, you don't even have to (but that
would be nice of course ;) to split the related tests (which I think are
already not separated in test_mass_import ;)