Fix inheriting of values
Improve name of observing source for easier debugging
Fix issue with layout when using percentage heights

It was incorrectly leaving _hasOwnHeight as false, even though a percentage of a
fixed size container should set it to true.
When height changes, set parent's needLayout to true
Propagate values in HSSMultipleValue
Fix layout issue when all the objects in a group have height 0
Remove redundant calls to setInnerHeight and setOuterHeight
Improve efficiency by reusing computed values instead of always substituting
Handle multiple values earlier in the pipeline
Don't set default text

It would overwrite the one set when the xml was parsed
Propagate hostProperty to the parser node in HSSValue
Clean tracked observers in each of the expressions
Only observe members of an expression if they are potentially going to change
RefFunction: copy values instead of storing/propagating the same ones
Remove dead code
Cascader: Commit the stack values of text blocks