[WIP] Support relative project package imports

I'd love having relative project imports, as I'm tired of rewriting all the settings for my custom mods in every project.
`LOG_FORMATTER = 'testproject.logformatter.MyLogFormatter'` needs to be renamed to
`LOG_FORMATTER = 'realproject.logformatter.MyLogFormatter'`,
`LOG_FORMATTER = 'nextproject.logformatter.MyLogFormatter'` and so on.
Would be nice to have relative imports here and just write
`LOG_FORMATTER = '.logformatter.MyLogFormatter'`.

I really hope there is a nicer way of doing it, than what I have here, though.
Any suggestions for improvement?