Add ES field for latest_dev_release_when_no_nondev_latest

[ranguard]

We want dev releases to appear when there has never been a full release.

So order to return dev releases, for releases which have never been authorised (in 06Perms) we need to add an additional field which is determined as follows:

• If there is NO latest (we ignore backpan) release, find the dev release with the greatest version number and set this flag to true on it (remove it from any others)
• As soon as there is a latest release, this flag should be set to false on all any dev release with it set.

Update the search so that this flag is included as an or against status = latest for latest_dev_release_when_no_nondev_latest

[oalders]

is_latest_pure_dev_release?

[mickeyn]

none of the current boolean fields have a 'is_' prefix... so for consistency, maybe: latest_pure_dev_release?

[Grinnz]

This would be really nice to have since we won't be able to rely on cpansearch for finding such modules anymore.