+sourceadmin UI for importstatus

[David Allouche]

The $productseries/+sourceadmin page provides inappropriate control over the importstatus.

There are currently two checkboxes at the bottom of the page to set importstatus to PROCESSING and SYNCING.

Instead, there should be:

One checkbox with the text "Import and publish branch" that is displayed if the importstatus is TESTING, AUTOTESTED or TESTFAILED and not initially checked. Checking this box will set the importstatus to PROCESSING and set the appropriate timestamps. It would be equivalent to the existing checkbox with the text "This source is certified for synchronisation".

One checkbox with the text "Do not import" that is always displayed. It should be initially checked if the importstatus is DONTSYNC or STOPPED. Checking it would set the importstatus to DONTSYNC if it was TESTING, AUTOTESTED or TESTFAILED, and would set importstatus to STOPPED if it was PROCESSING or SYNCING. Unchecking it would set the importstatus to TESTING if it was DONTSYNC, and would set the importstatus to SYNCING if it was STOPPED.

Downgrading to autotest is postponed until importd-ng to avoid race condition with importd.

The changes should be applied (conceptually) in the following order:

1. import-and-publish
2. do-not-import

The existing checkbox that is only display when imporstatus is TESTFAILED must be preserved. It's good.