for inserting macros into the config. The new method is much cleaner
and uses the Config API.
Updated the docs for the RootTitle macro, both POD and online help.
Session/Id.pm: add a method to validate GUIDs, change s/// to tr/// for efficiency.
Session.pm: change open to use new Id.pm validation method
Scratch.t: Change test from ok to is so that it tells you what the failing ID is.
Id.t: Add validation tests in addition to uniqueness tests. Fix the uniqueness test so that it works. Add tests to check the new validation method