Update backend to somewhat work with metadata v0.4

This needs a lot more work, but at least runs.

Remove search by type. This had to be done because
type was changed to learningResourceType, which is
a free string and no longer an enum.
String search for type could be added in the future.

Disable suggestions for format. This was done because
in the current version format is no longer a list
but a single string. There are problems with that, so
this might change again.

Lots of tests fail.