Have backendContext module return baasUrl

[jjohnstonspm]

It'd be nice if the backendContext module could return metadata.baasUrl. As it stands, to invoke REST API calls from a Flex Function, I need to also pass around the context object (to get "context.headers.host"). For example, see the example in the Flex API reference:
https://devcenter.kinvey.com/rest/reference/flex/reference.html#Examples5