Making standard.ipn tests pass.

On MySQL, ordering by date does not give the desired ordering of getting the
most recently inserted row first. We need to order by the primary key too.
Merge pull request #14 from MTsoul/master

Making tests pass for standard.ipn for MySQL.
add signals and tests for recurring_skipped, recurring_failed ipn
change file permissions
make the recurring_payment test into a negative test case, this signal is never called by the code because this ipn has a txn_id
make tests work in isolation by removing and replacing all signals
Merge pull request #15 from jasonculverhouse/master

Added signals for recurring_payment_skipped and recurring_payment_failed
remove redundant use of recurring_failed
Merge pull request #17 from jasonculverhouse/master

Fixed use of recurring_failed in the ipn_tests
Improved IPN tests to post data the way PayPal does
Handle saving of query the way PayPal needs
Fixed encoding problem for parameters sent in PayPal IPN POST data
Corrected comments on some fields on standard model
Handle Paypal missing payment status types.

The following payment status types are being added:
- Canceled_Reversal
- Refunded
- Reversed
- Voided

The payment_status field in PayPalStandardBase is being
modified. The max_length is now 17 to handle new types.
Corresponding migrations for ipn and pdt exist.

The following new IPN signals are being added:
- payment_was_refunded
- payment_was_reversed

The following new methods are being added to PayPalStandardBase:
- is_refund
- is_reversed

Added test for the new signals.
Ensure that _verify_postback passes through any flags set as the result of the postback verification to the PayPalPDTForm.

When a PDT trnsaction is flagged, the flags set (if any) are not passed to the form that is used to update the pdt object.
This commit fixes this issue.
merged commits from atul-bhouraskar
merged repo from spookylukey