Add section for UI Domain design principles
Add section for UI Domain design principles

Separating it from general design principles that should hold for all
the codebase, and from problems specific to the Database domain.

vacationlabs/haskell-webapps,meditans/haskell-webapps,vacationlabs/haskell-webapps,meditans/haskell-webapps,meditans/haskell-webapps,vacationlabs/haskell-webapps