Is there a function or library to EmitFrom a Mesh or Object for the Particles?
Not that I know of right now. You can only use the presets which are selectable in the drop-down menus. Usually it's spheres, planes and boxes... not sure how hard it would be to implement a polygon / shape-based particle emitter.
Indeed, we're working on that effect right now. Should be upcoming with one of the next versions.