Add route to create Collection

We should create an resource `/api/collections` to manage collections.

The collection creation should cover:
- Bands definition
  - With vegetation indexes (use `metadata` property. See more in [`bdc-catalog#bands-metadata.json`](https://github.com/brazil-data-cube/bdc-catalog/blob/master/bdc_catalog/jsonschemas/band-metadata.json)
- Add entry in `bdc.quicklook`