Add mod count to mods page

[Trial97]

Fixes #451

[getchoo]

i'm not exactly sure what's going on here: in my testing the mods page (and only the mods page) will have the install/select count appear when you first view it, but if you switch to a different tab like resource packs and go back, it won't appear at all until you have selected a mod.

[Trial97]

I fixed the mentioned comment but in order to fix all of them I removed a line that was prefixed by the following comment:

// Prevent a weird crash when trying to open the mods page twice in a session o.O
disconnect(mods.get(), &ModFolderModel::updateFinished, this, 0);

I could not get it to crash as the description is vague. But if somebody knows why that line was added let me know.

[getchoo]

it seems @flowln was the one who left this (sorry for the ping, not sure who else to ask :p). could you shed some light on this so we can see if it's still needed?

[flowln]

The description isn't vague, it is just as simple as it sounds: Without that line, it used to be the case that the application would crash if you opened the mods page, switched pages, and returned back to the mods page. I suppose the underlying cause of the crash got fixed at some point, so the line doesn't do much now. Nice!

Also, you can probably remove mods from the lambda now.

[getchoo]

thank you so much! just wanted to make sure :)

[getchoo]

i just tested this again as well and it seems to good to go! the only other thing i would recommend is following flow's suggestion

[DioEgizio]

seems to work as expected

[getchoo]

thanks!