Add rest endpoint for create_from_source_index

[parkertimmins]

Add rest endpoint for create-index-from-source action. This endpoint will create a new index using the settings and mappings from an existing source index. Setting and mapping overrides can be added to the request which will override settings and mappings from the source index.

Request
Method: POST or PUT
Path: _create_from/{source}/{dest} where source is an existing source index and dest is the name of the index to create.
Body can contain settingsOverride and mappingsOverride which are standard setting and mapping objects which will be merged with values from source index.