Editor cancel adding new feature

[johnnyblasta]

Is your feature request related to a problem? Please describe.
It would be nice to be possible to cancel adding a new feature without leaving a empty feature which happens when using close button when using editor control in autosave/autoform mode.

Describe the solution you'd like
There should a save and cancel button in edit form. Clicking cancel should reove feature from map. Save button should save the attributes to the feature.

[steff-o]

Just a heads up: if autosave is true, the feature has already been saved to the server when the attributes form is displayed and has to be deleted remotely as well. The other approach would be delaying the autosave if autoform also is true, but that will probably break related tables and attachments as those rely on a real database id to exist when form is displayed.