setup.py: Try to make the missing dependencies list as visible as possible

Signed-off-by: Jerome Flesch <jflesch@gmail.com>
Support virtualenv installation for UI files lookup

I've also reorganized the lookup, so that the most useful entry is at the top for end-users. This avoid scary warnings ;)
Merge pull request #167 from Glandos/patch-1

Support virtualenv installation for UI files lookup
Merge branch 'testing' into unstable