BBasic writing of constraints
Test framework for constraintsolving
Add type checks to constraint writer
Move constraint writer to Artemis
Fix too many PCs recorded in the same session

Fixes #45
Make constraint writer fail silently.
Fix bug in type check for constraint writer
Improvements to testing framework for the constraint writer
Merge branch 'feature-path-exploration' of github.com:cs-au-dk/Artemis into feature-path-exploration