Inline constraints

This one contains all the remaining constraints except the Regex constraint which is not registered to work as inline constraint. I will add it as a separate commit/PR, it needs special handling as it depends on the behavior of not splitting the parameters on a comma. ( The code we had would not work as today we have two constructors for RegexConstraint)..More on this in the PR.
also `string.empty`

I found it a little surprising that by-default a 0-length string works here, we should have a test for it.