fix for test from assumed_default change to float
added default_value to passthrough trait metadata
framework_var for gradient option
Merge branch 'dev' of https://github.com/OpenMDAO/OpenMDAO-Framework into vartree_asmb_boundary
assumed default in int and enum
backed out some changed to driver from another branch
Added variable names to invalid variable error for constraints.
added assumed_default to bool
Moved unresolved variable check out of Constraint.__init__ and into ExprEvaluator.__init__.
Moved error generation to separate method.
Made expr a keyword argument. Default to using self.text
Made class method to create ValueError.
_invalid_expression_error expects expr and msg to be strings
Added documentation and fixed typo.
Made error message more clear for constraints and objectives.
Ignoring pyd files (python DLLs).
Fixing generation of error for Objective
Fixed test_hasobjective
Fixed errors in Constraint. Fixed test_hasconstraint.
Connection expression error message reports all invalid variables.