Contributions with "In Progress" status can't be edited and saved

The 'In Progress' status was only intended for use w/ Pledges, but was previously exposed in the select box for contributions. In 4.3 this status was suppressed in the contribution form, BUT the backoffice Membership and Event Registration forms STILL allow users to assign that status to a contribution. Users are making use of that to represent partial payments.

Changes made in 4.3 block transitions from that status to any other status with a form rule error on the contribution form (see attached screenshot). So users can't edit / save any contribution that was created with In Progress status.

To recreate:

• add New Membership via backoffice form and set payment status to In Progress
• now edit the newly created contribution
• the status will appear to be Completed (since the actual 'In Progress' status is not available in the dropdown).
• try to save the contribution as 'Completed' - form rule error is thrown:

Cannot change contribution status from In Progress to Completed.

Also 2 notices:
Notice: Undefined index: In Progress in CRM_Contribute_BAO_Contribution::checkStatusValidation() (line 2879 of /Users/dgg/git/crm_v4.4/CRM/Contribute/BAO/Contribution.php).
Warning: in_array() expects parameter 2 to be array, null given in CRM_Contribute_BAO_Contribution::checkStatusValidation() (line 2879 of /Users/dgg/git/crm_v4.4/CRM/Contribute/BAO/Contribution.php).

One approach to fixing this:

• continue to allow In Progress "work-around" by leaving that status as an available option in Participant and Membership forms
• modify CRM_Contribute_BAO_Contribution::checkStatusValidation and the underlying account transition code to handle In Progress => Completed transition
• modify API as needed to allow In Progress => Completed transition via api as well (see http://issues.civicrm.org/jira/browse/CRM-14022

Going forward, we can potentially migrate 'In Progress' contributions to 'Partially paid' (4.5)