[Feature] Skip web hook enabled modules in bot

[HebaruSan]

This is an outgrowth of KSP-CKAN/CKAN#2789 (comment). I assume that the initial functionality of the queue-based bot will be identical to NetKAN-bot, so ideas for further improvements should be submitted here for better tracking.

Motivation

If a mod's $kref is on SpaceDock, our web hook will be notified of new uploads immediately, making the bot redundant some of the time. If a mod has a $vref property, then it's still necessary to crawl it, as its KSP-AVC version file may have a "URL" property pointing to a supplemental remote version file that could be changed at any time without notifying any web hook. But if there is no $vref, then the web hook should be sufficient by itself.

Suggestion

If a module has a SpaceDock $kref and no $vref, it doesn't need to be added to the queue for inflation. Skip it.

There are 789 such modules, or about a third of the total, so this could cut the bot's total CPU load significantly.

[techman83]

I like this idea!