prune unused variables in StrZ3 (maybe useful in others, too)
handle unused variables in unary operations
add soft constraints to commandlineZ3, also add tests and tests for StrZ3
remove bogus classes
update z3 with soft-constraint branch and latest unstable
hack cassowary to throw actual errors, so we see them when using the workspace
use soft constraints only in CmdlineZ3 for now, strip useless errors, and try to fix the path issue on firefox