fixed PsiInvalidElementAccessException for invalid elements stored in PythonPathCache

clear PythonPathCache on pushLanguageLevel
fixed PY-14538 BUG: Invalid IPython Notebook generated by PyCharm 4.0
fixed PY-6518 Editing name of Python interpreter doesn't repaint "Python Interpreters" dialog
Merge remote-tracking branch 'origin/master'
fixed move cell up location in keymap
removed wrong local imports from builtins

updated mock sdks
Merge remote-tracking branch 'origin/master'