Fixes bug when saving amazon payment.
Prevents amazon payments from importing the same transaction twice.
Changes payment schema to use integers instead of decimals.
Updates amazon payment for changes to payment module.
Fixes bug causing csv system to skip last line.
Adds billing form and tab.
update payments & contributors

added "other" payment method, fixed spelling of cheque & updated
contributors file
Added a comment to the 'amazon_payment_contact_table' function.
Fixes bug in payment_save() caused by missing quotes.
fixed bug where payment editingdid not save redit and debit cids.
Fixes formatting bugs in payment module.
Adds crm_get_form() to core for generating form structures.

Allows other modules to alter the form structure.
Fixes bug in crm_get_form() that caused $form_data to be empty.
Links amazon name and contact when an amazon payment is edited.
Fixes bug in parsing value of edited payment.
Completes billing functionality in billing module.
moved billing from plans to payments, fixed perms
Changes amazon payment import to check for existing contact mapping.
Added ability to user email as user authentication; closes #16
Updates copyright date and email.