can't change page url

[SotiriosVrachas]

How to reproduce:
create a page
set title and url
save it
change the url

[PunkChameleon]

This was 👍 by @Capox.

[PunkChameleon]

The reason why this is this way currently is that the page_url is base64'd into the ID, and that info is used throughout the application.

I'm definitely not enamored by this, and I think it'd be better to create the ID another way (maybe the UTC long of when it was created?) and allow all this info to be editable.