allow many attributes to be added via the UI

[terraswat]

Initially, just a way to add many attrs dynamically without saving them to the map would be useful. Currently, 50 or even fewer is too much memory for the shortlist. Under some browsers 50 will load but the shortlist is too unresponsive to be of any use.
Longer term, Josh and others have asked to be able to add 50 or 100 dynamic attributes.
Also, some have asked to be able to add attributes permanently via the UI.