Begin endpoints for glacier metadata.

Tests to follow.
Test metadata logic in models and views.
Merge branch 'develop' of https://github.com/CenterForOpenScience/osf.io into feature/osf-storage-glacier
Merge branch 'feature/osf-storage-glacier' into develop
Merge branch 'develop' of github.com:CenterForOpenScience/osf.io into feature/treebeard