Generate PS types of API endpoints (#199)

[sectore]

by using purescript-bridge.

Plus:

• Extract content of Guide.Api into Guide.Api.* modules.
• Add custom client types to simplify bridging types from HS to PS.
• cherry-pick of be77f89d0761da1c332f7a0cc2fde79b441f733d

How to test?

1. Generate types

   ./b
   stack exec guide-hs2ps 

2. Build PS stuff

   cd front-ps
   yarn build