Fix idea project resource patterns.

For a project that has a number of various resource files, this will now
generate:

"?*.json;?*.creds"

Rather than

?*{'.creds?': True, '.json': True}

Which Intellij (12) cannot interpret.
Remove site-packages from sys.path for pex files.

Pants makes a (somewhat feeble) attempt to scrub site-packages out of
the
sys.path in an attempt to have an 'hermetic' system.
This fails pretty badly on some of our osx installation, and this simple
hack improves its accuracy.