Allow people to create their own page

[aquatix]

As you can already kind of do so by just randomly enter a URL and start adding bookmarks [1], allow people to create a page on their own.

Preferably by using something like https://github.com/trezor/python-mnemonic for more friendly url's, or offer the choice between that and a more secret random string.

This can easily be implemented by a button on the homepage of a digimarks installation.

[1] which is slightly buggy as you don't have a User object, so you can't create public tag pages