Fixtures with Attribute support

[Feature-spec](https://docs.google.com/a/dimagi.com/document/d/1yVSotTa33_UF9dd5iuRYc80FbkqP6sIWGiiPaAP_gVQ/edit#heading=h.v1gf9mhs7nhi)
- Fixtures are now called Lookup Tables 
- Items in Lookup tables can now have attributes. Sample output of [OTA-restore](https://gist.github.com/sravfeyn/d974ff89eb3bc362f379)
- Most of Edit-UI is removed and [UI](https://staging.commcarehq.org/a/sheel-test/fixtures/edit_lookup_tables/) is [changed](https://staging.commcarehq.org/a/sheel-test/fixtures/view_lookup_tables/)