Per-collection configurability via STAC

We could extend the catalog per-layer configurability by allowing generic passing of map, source and layer parameters directly via STAC item and collection metadata utilizing `eodash:` prefix.
A new functionality would be that arbitrary parameters can be passed in and will be only for experienced data administrators who need large flexibility (up to the level of everything that OL sources/layers support out of the box).

connected issue https://github.com/eodash/eodash/issues/347

No files, tests, or entry points are named. Start by reading connected issue #347 and tracing how STAC item and collection metadata are consumed; done means arbitrary eodash-prefixed map, source, and layer parameters can be passed through with the intended collection-level configurability.

Written by the indexing model from the issue text.