Updating external licenses to reflect latest changes
Merge remote-tracking branch 'upstream/master' into updated-licenses
Merge remote-tracking branch 'upstream/master' into updated-licenses
Merge pull request #149 from oxtopus/updated-licenses

Updating external licenses to reflect latest changes
PIL removal

remove obsolete PIL/Imaging/Python Image Library,
it was used for image recognition, is now unsupported
and obsolete.

Used eg in people-tracking-demo
PIL add notice to demo using PIL

maybe it got broken, well, it's broken anyway
remove libpng

was used as dependency of PIL (obsoleted too)
mention PIL in requirements.txt for pip

Conflicts:
	external/common/requirements.txt