Add Emulator Provider

[alexdebrie]

Adds a provider for the emulator.

To add an emulator function:

{
  "functionId": "helloWorld", 
  "provider": {
    "type": "emulator",
    "emulatorUrl": "http://localhost:4000",
    "apiVersion": "v0"
  }
}

@mthenw Feel free to change it to your liking 😁

[mthenw]

@alexdebrie thanks for contribution! FYI, I've made few changes.
@brianneisler thanks for fixing lint errors.