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
remove simplejson module, use (standart) json instead

since python 2.6+ simplejson is included in standard python lib as json module.

there are speed disputes: http://stackoverflow.com/a/16131316/78234
but measuring our usecase, .dumps() is used (slightly) more ofthen than .loads(), so json is faster.
Also, bug-fix support is better for json.
update files to import json instead of simplejson
tweepy installed by pip

before was only on Linux, now on both platforms
PS: why is this used? :)

use version=2.1

Conflicts:
	external/common/requirements.txt
psutil installed by pip

version 1.0.1 used

Please test on MacOS, there were some .so files present there...?

Conflicts:
	external/common/requirements.txt
remove unused Crypto module
remove compiler links to -lcrypt

Crypto lib is unused, dont link to system version either
YAML installed by pip

was external/linux64(darwin64)/lib/python2.6/site-packages/yaml
pip package is PyYAML
there's also a folder with C files: external/share/yaml-cpp
Updated licenses
Merge pull request #3 from oxtopus/updated-licenses

Updated licenses, thanks for review! Licenses merged.
Merge branch 'master' into modular-PIL
Merge pull request #140 from breznak/modular-PIL

Modular PIL - pip'ed and obsoleted
Merge branch 'master' into modular-python-modules

Conflicts:
	build_system/post_build/files_to_copy.txt
	external/common/requirements.txt
Merge branch 'modular-python-modules' of https://github.com/breznak/nupic into modular-python-modules
Merge pull request #146 from breznak/modular-python-modules

Modular python modules
Merge remote-tracking branch 'upstream/master' into npc-73
Adjusted for moving sortedJSONDumpS() into the nupic.support.serializationutils module