Initial integration of QTI and IMSCP import

• Does an initial integration of IMSCP import into ricecooker.
• Adds some simple utilities for mapping IMSCP/SCORM metadata fields to our metadata
• Allows proper mapping of embedded webcontent files to the entry option
• Writes tests to cover this behaviour

Fixes #332 Fixes #337

Looks like the way I am doing the zipfile testing is not compatible with Windows, open file handles etc - will need to update for that.

I've been playing with the latest code from this PR:

• Ricecooker works
• Uploading to Studio unstable works
• The channel appears correctly (preview doesn't work, but that's not a ricecooker problem) https://unstable.studio.learningequality.org/es-es/channels/6877a75b029e5259a02c93046ee6dd80 , token: kokom-fitih
• Using kolibri v0.16.1, I can see the channel, the structure is a bit weird, with more levels than expected: 1 single scorm file has up to four levels to access to the resource:
• After importing it, it does not work correctly, this is the error message: