Feature request: separate SDK source from name #1066

Reserving prefixes for certain types of SDKs is confusing, e.g. #1065. I suggest we add a new optional field:

sdks:
  - name: try-sdk
  - name: project-sdk

becomes

sdks:
  - name: sdk
    source: try
  - name: sdk
    source: project

(this is what it deserializes to internally, anyway).

Some implementation details:

• channel != "" should only be compatible with source: store (the default)
• name: system and name: sketch imply source: system and source: sketch respectively, anything else is a conflict.