Modifying Python routines for Python 3

So far only changes to print:

print ""  -> print("")
Small bug fix to Python collect

When finding a variable name, the original name was
returned, rather than the corrected one. Only mattered
when an invalid name was used, and resulted in failure.
Merging Python3 changes

Modified print statements only

Conflicts:
	tools/pylib/boutdata/collect.py