added "Private" attribute to Grants

Private grants are only viewable by Organization admins, whereas public grants can be seen by all organization users.
Refactored views. Private attribute still WIP
Non-admin users can see their assigned tasks only
Merge branch 'permissions' of github.com:omahacodeschool/grant-tracker into heather

Conflicts:
	app/views/pages/_dash.html.erb
	db/schema.rb