Update all donation permissions to take into account redhen namespace.

“donation” by itself is potentially too generic.
Support any entity URI when appending donation local tasks.

The old approach only allowed for entity_type/entity_id patterns.
Fix permissions key.
Fix permissions key.
Remove unused function.
Fix permissions key.
Fix borken constructor.
Create a helper function get a formatted donation amount.

Removed duplicate code.
Fix incorrect/inconsistent use of metadata wrapper in hook_commerce_payment_order_paid_in_full().
Coding standards in redhen_donation.module.