! Add Personal Text to the list of standard profile fields, incidentally...

... this makes the field available on registration, as an option. Because of conflicts with the ability to set default text, setting default text is only available when the field is enabled and not shown at registration (the default). We *could* amend birthday to be disabled but we probably shouldn't, we can revisit that in future, which means this should resolve #301.

Signed-off-by: Peter Spicer <sleeping@myperch.org>