Adds a default date to the next first of months in contracts.
Improve the Manual Reconciliation Process by:

- Adding buttons for opening custom wizards
- Adding button for opening current partner

Fixes:

- Related contracts in reconcile wizards not
  properly retrieved.
Improvements on the contract views.

- [FIX] A simplified tree view in module reconcile_compassion was
        overwriting normal tree views. Now it is a separate view.
- [ADD] Frequency in contract tree view
- [ADD] Contracts in partner view are sorted on start_date
- [ADD] Contracts in partner view can be opened on current window.
- [FIX] PEP8 errors.
Added buttons to go to transactions and unreconciled move_lines from the
invoice view, to ease the verification of generated invoices in
account_statement_completion_compassion module.
Fix PEP8
[NEW] Added a wizard to generate Gift Invoices from an active contract.

It can be useful when a sponsor used a sponsorship reference in order
to pay for a gift. In this case, the user is able to create a gift
invoice in order to reconcile the credit.
Removed dependency on module account_banking_payment.

Extracted the ability to filter invoices collected in payment order by
payment term from the module account_banking_payment and included it
in module lsv_compassion, so that we can remove dependency which avoids
installing a lot of functionalities we don't use, and avoids installing
module account_banking which brings a lot of mess in accounting views.
PEP8 + headers correction on module lsv_compassion
Modify activation of contracts called by GP so that they can be activated one at a time (more reliable).
Removed useless pdb import
Small bug fix.
Corrected missing context in method.
Bug fix where view_id of invoice_view was the same as statement_view in module completion_compassion
Bug fix where it was not possible to unreconcile invoices.
New clean_invoices method that takes care of invoices paid in advance.

When a contract is cancelled, if there are paid invoices in advance by
the sponsor, it will :
	- cancel them
	- remove the invoice_line of contract
	- split payment and reconcile if possible
	- if not possible, put a move_line name that will warn the person
	  doing the manual reconcile.
Corrections on contracts cancellation.

- Invoices cancelled keep their lines so that we can see what was
  the invoice.
- Several bug fixes.
- Start date can be rewinded if the contract is in draft state.
Updated translations
Modified next_invoice_date calculation to consider only active contracts.
Cron bug fix
Bug fix in bvr_ref_compassion, PEP8 and Headers