platin: update roadmap
platin: revert bad API design decisions (use program points instead of Reference(s))

This patch gets rid of the Reference class in platin (and all subclasses), which
represented context-free program point references. All references should be ContextRefs
now.
platin: add options to pml tool for inspecting the PML database
platin: update run-tools demo
platin: refactor AIS program point export
platin: update installation script (should find user-local gems now)
Merge branch 'master' of https://github.com/t-crest/patmos-llvm