Extra sources into a subdirectory of the module

[axtloss]

vib currently fetches any sources directly to /sources, this can cause issues when sources (mainly tar sources) do not contain a seperate root, meaning all the files from the archive are extracted directly into /sources.

A better way to handle this would be by creating a subdirectory for every module in which the archive is extracted, in addition to a new Sources property which lets users specify an extra subdirectory to extract sources to.