Update frontend to handle a metadataType refactor

[petterroea]

Short description

As MetadataType now is just a node in a tree, i have refactored it so it uses an Uuid as unique identifier. However, this causes breakages:

• Change the "Create metadata type" page so you have to select the metadata category it belongs to. Maybe this needs to be a tree viewer as well
• Maybe show the category a metadata type belongs to on the "show metadatatype" page
• Take a good look around for breakages. Not really 100% sure all the places this will cause a breakage, but anything that relies on a request from /api/MetadataType is probably broken

Dependencies

#201