mitxmako => edxmako
settings.MITX_FEATURES => settings.FEATURES
mitx_markdown => edx_markdown
MITX_ROOT_URL => EDX_ROOT_URL
Update logging.getLogger() calls to use edx instead of mitx
update npm package name to edx
Updated test strings to refer to edX instead of MITx
Updating tests, comments for MITx -> edX transition

Also whitespace changes