[SDL 0219] Explicit returned type from NSDictionary(Store) category

[theresalech]

Proposal: Explicit returned type from NSDictionary(Store) category

This proposal is to specify returned types from NSDictionary (Store). This ensures that the return value is assigned to a variable of the correct type.

Review: smartdevicelink/sdl_evolution#685

Steering Committee Decision:

The Steering Committee voted to accept this proposal with revisions. The Revisions will include changing the method signature to the one that returns an error noted in this comment, so in the case of an error the NSError object could return the original data and an error message, or in the future, a fallback object for mandatory parameters.
The revisions will also need to state that optional parameters will log the error and assert in DEBUG, then return nil, and for mandatory parameters we will log the error, and assert in DEBUG, but will continue to return the bad object for now.
The proposal .md file was updated to reflect these revisions on 3/19/19.