bit of work converting D.Core.Types
more work on fixpoint conversion (still not compiling)

next task: semigroup/monoid instances for RTrees?
yet more work on fixpoint conversion.  Remove SubMap for now.  Functor/Transformable instances.
Merge branch 'fixpoint' of github.com:diagrams/diagrams-core into gsoc

Conflicts:
	src/Diagrams/Core/Types.hs
Remove Names and SubMaps from the context
Add function to find a path inside a tree
Merge workstation:dev/diagrams-core into gsoc

Conflicts:
	src/Diagrams/Core/Types.hs
Add Environment to Context
Add above/below to explore environments
Add PathM-based editing functions