Change Log 2013-12-30-A

Manhy changes in this revision:
1: Payment form modified to allow processing of off site bookings
2: Refactored error handling code for dates
3:  Added new constants and modified soe string constants
4: Code clean up and refactoring inside webform_ext_funcs.inc
5: Added new function _wwebform_ext_get_mail_key
6: Modest updates to webform_ext_forms.js
7: Modified mail hook function to add new keys and remove replaced key