allow defining 'defaultSolvers' and we pick one that works
WIP: re-arranging regions for assignment
update Thermometer example, you can now edit the text strings
refactor visitBinaryOp, use the simpler code to provide informative errors for alternative operations
collect error messages when trying solvers; don't constrain strings
test for last commit
fix references, indenting, and 'first duplicate' bug in source code transform, add tests
Merge branch 'master' of https://github.com/timfel/babelsberg-js

Conflicts:
	babelsberg/constraintinterpreter.js