start porting to python2

this file will describe progress, please help/test from this branch!
porting to python2 (2.7) so NUPIC runs on systems where default python is python3.
This is no shortage of "too specific" python, as porting to python3 is more difficult
and will demand more then just renaming a few lines, so I dont expect it that soon.
build: formatting, only use #!/usr/bin instead of #! /usr/bin

this is just a cosmetic change.
command to produce this is:
 /usr/bin/vendor_perl/ack -f --python | xargs perl -i -p -e's@#! /usr/bin/env@#!/usr/bin/env@g'
after #! refactor, keep check for both #! and #!<space>

manually fix check for both acceptable cases for shebang
refactoring use python2 : rename all #!/usr/bin/env python

this is first part of refactoring to use python2 instead of python
(python can be python3 now or in near future)

command for this rename:
 /usr/bin/vendor_perl/ack -f --python | xargs perl -i -p -e's@#!/usr/bin/env python@#!/usr/bin/env python2@g'

PS: ack is something like find+grep
manual fix for specific occurence #!<space> python2

this is only 1 occurence in all codebase, all other have been
automatically translated,
refactoring: replace python -> python2 in all shell files

command
/usr/bin/vendor_perl/ack -f --shell | xargs perl -i -p -e's@python @python2 @g'
refactoring: manually fix "python" usage in comment

for previous commit
refactor python2: replace 'python' *.py usage in python files

command used:
/usr/bin/vendor_perl/ack -f --python | xargs perl -i -p -e's@python (.*\.py)@python2 \1@g'
refactor python2: manually fix after prev, commit

in two files:
external/darwin64/lib/python2.6/site-packages/pkg_resources.py
external/linux64/lib/python2.6/site-packages/pkg_resources.py
refactoring python2: replace python->python2 *.py in all other files

command:
/usr/bin/vendor_perl/ack -f | xargs perl -i -p -e's@python (.*\.py )@python2 \1@g'
refactoring python2: final review and manual fix

to review rest 'python ' usage, do:
/usr/bin/vendor_perl/ack -f | xargs grep -e'python ' |grep -v proj|grep -v python2| less
Revert "start porting to python2" - finished!

This file/commit was a placeholder and info, everything seems done now,
so reverting this and head for inclusion. Please test!
This reverts commit c912dd57e3efcb2a2dbaefd6ea910d4b7cdd736c.
reviewed remaining changes