Stub out 2.0 API

[nkolba]

• [x] support switching API from 1.2 to 2.0
• [x] internalize interfaces for 1.2 (to support npm update of @finos/fdc3)
• [x] update @finos/fdc3 package
• [x] get all type errors resolved (don't worry about functionality just yet ;))

[nkolba]

fixed with PR #78