Improve Administrator Panel

Significant functional and display improvements to charity administrator panel

![adminpanel](https://cloud.githubusercontent.com/assets/8646429/5247704/cd13751c-7942-11e4-8900-5966f2a06cb4.gif)

``` ruby
availabilities_grouped_by_date.inject(0) do |sum, (_date, availabilities)|
  sum += availabilites.confirmed_pickups.map(&:count).inject(&:+)
end
```