Framework Support for Stack & Cabal

[LeanderK]

#298 introduced an abstraction that makes this issue relative straightforward to resolve.

it just needs:

• implementation of FrameworkTypeEx for each
• toolbox to create/add/remove projects (stack) and packages (cabal)
• wizards for importing stack-projects (stack, is already existing for the import project action) and cabal-packages (may reuse parts of Discover Cabal-Packages)
• remove AddCabal/DiscoverCabal Action
• register framework support for new-project/import project from existing sources action
• remove HaskellCompiler setting, replace it with a general stack/cabal setting. Delete mainProject in system.packages