Proposal: a URL/URI TraitType

[corranwebster]

This would be straightforward to write using the standard library URL parsing module. Would potentially be useful in a number of places, most immediately for things like the HTMLEditor in TraitsUI, but also for code that is interacting with servers of various sorts.

This is a nice-to-have, not essential.

[mdickinson]

:+1: I think this would be useful in a lot of current and future ETS-using projects.

Tentatively targeting 6.2.

[mdickinson]

Not for this release