Feature Request: Implement Feature Events for Grid Feature and other Features

Currently the tasks available for features are limited to events generated by layers:

https://opengeoscience.github.io/geojs/apidocs/feature.js.html#line155

I would like for the relevant feature events described in the documentation to be available: geo.events.feature.mouseover, geo.events.feature.mousedown:

https://opengeoscience.github.io/geojs/apidocs/geo.event.feature.html