Factor bind/observe Property/Get

And deprecate observeKey. Use observeGet.
Throw error for unmatched close paren

Test for parse errors.
Silently stop propagation of unparsable evaluate
Ignore null parameters in evaluate
Ignore non-observable ranges in content binder
Coerce range length to integer

This fixes a bug in shrinking a range to a floating point length.
Update collections version predicate
0.1.17