Limited instalments

I've made some changes which I should probably have broken into smaller chunks. I apologise for bundling them all into one PR.

This is what I did ...
 - Made the code comply with CiviCRM 4.4
    - CRM_Core_BAO_MessageTemplate
    - next_sched_contribution_date
 - Captured the eWAY Transaction Number in the Contribution record
 - Added update_recurring_contribution() function to standardise update logic ...
    - if the number of instalments is limited (eg, 12 instalments), and the next
      instalment date would be beyond the date of the last instalment, then
      Complete the Recurring Transaction, and set its end date
 - Changed complete_contribution() to capture eWAY Transaction Number
 - Added more define()s for Contribution Status