Add Regular Expression strings to NamingConstraints

[drewlyall]

Modify NamingConstraints to allow the specification of regular expression strings for client field validation.
Also adding "lastCharacterXXX" allowed attributes would help with certain clouds that don't like symbols as the last characters.

[drewlyall]

I've added the related fields to the NamingConstraints object but they're not included in any of the validation yet.