Add download count column to GUI

[HebaruSan]

Motivation

KSP-CKAN/NetKAN-bot#67 created a script that updates a download_counts.json file in CKAN-meta containing the download counts of mods. This data is available now (and already being downloaded whenever anyone clicks Refresh!), but it's not being used yet.

Changes

Now when you refresh the registry, we extract the download_counts.json file and parse it, then store the values it contains in a dictionary at Registry.download_counts.

A new Downloads column is added to GUI displaying this value for each mod. The user can sort this column to identify major mods that they haven't tried before.

Congrats to KIS for winning the popularity contest:

Correction: Congrats to EVE for winning the popularity contest (now that KSP-CKAN/NetKAN-bot#73 is counting older branches):

Fixes #2415.

[yalov]

tested, works ok 👍

@StollD @techman83 Is it possible to add to spacedock API "downloads per versions" for making this more dynamic?

"all downloads counts" makes it less "popularity" and more "how often mod was updated, and how many bug-fixing releases there was".

May be count popularity as maximum of the downloads of the last 2 versions?

It does neutralize the above problem, the last-hour-release fall, and get KER back in the row,
but then some popular rarely updated mods will dominate

relative - KSP-SpaceDock/SpaceDock#185

[HebaruSan]

I don't think that EVE, KIS, CRP, Firespitter, KER, B9, and KAC have high numbers because they release lots of bug fixing updates. The current statistics turn out to work well in practice.

Think about it. If you downloaded a mod that turned out to be low quality (i.e., doesn't deserve to be "popular"), would you download lots of bug fixing updates for it? Or would you uninstall it
and forget about it?

[yalov]

EVE, KIS, etc would be "popular" for every counting system.

But when Universal Storage II overcome Universal Storage, or SSPEredux overcome SSPE, in few years? I think they are already popular.

For a new mod to be qualified as popular (with all_downloads) is not about quality, but about how long a mod is bouncing around.

if mod1 and mod2 is used by equal amount of people, but mod1 has 20 updates since 1.2, and mod2 is new (2 update since 1.4), then I don't see them as "mod1 10 times more popular than mod2"

Also mods popularity changes. A mod was popular but then a better mod, doing the same was out, and it stole users — all_downloads doesn't care, at least quickly

[HebaruSan]

Would you mind filing your suggestions as an issue?

https://github.com/KSP-CKAN/NetKAN-bot/issues/new

I don't want to give the impression that we're debating the simple GUI functionality in this pull request.

[politas]

With all these extra columns being added, I'm starting to feel a need for the ability to hide columns.