Update Open edX to Maple version

Blocked by #83 (closed) because it's probably smart to update to Lilac.3 first.

Release notes: https://open.edx.org/blog/maple-has-been-released/

Remaining issues:

• Totem theme broken indigo-totem#36 (comment 116759) Added as dependency
• Investigate why no language selector with MFE
• Check if forum works
• Activation links doesn't seem to work? Tried opening it in the wrong browser
• Add apps. subdomains to Deflect
• I saw there was an update for the video xblocks?
• Check if xblocks update is working (doesn't seem to be, issues with logs)
• Why openedx-i18n still mention Lilac? Can we try changing it to Maple? (Yes we can, outputs exactly the same thing)
• Verify Farsi translations
• maple.2 which should arrive super soon Let's not change too many things at once. Maybe by the time we're done nutweg/nutmeg will be released so it will be more efficient to switch to it
• Check for other things that might be broken
• See how to make use of MFEs without the MFE plugin