Refactor/remove phase from motion

Removed phase from motion as we no longer need the state machine to reopen motions.
Migration removes column from table.
Created new methods open?, closed?
Merged methods close! and close_motion!
removed motions_closed and motions_in_voting_phase scopes in group and user, replaced with methods closed_motions & open_motions(These did not work as scopes for some reason. Maybe something to do with the Time.now?)
Removed unused scope open_votes.