changed Practices to Events

practice changed to event date
beginner changed to guest
added generic calendar and member icons; added shellViewController to control tabbar icons; settings is opened from shellViewController by both tab bars
added checked/unchecked icons
changed member/payment status to colored border with rounded corners
fixed scoping for payment and attendance on organization; fixed query to include organization for payments
Merge pull request #24 from bobbyren/genericIcons

Generic icons