Ability to clear auto-installed flag from changeset tab

[HebaruSan]

Motivation

The Changeset tab is shown when you choose to install, upgrade, or uninstall mods and then click Apply. If there is something in the list that you don't want, the only way to fix it is to click Back, then scroll or search through the mod list to find the affected mods, then make whatever change would undo the change, then click Apply again. This is cumbersome, especially for auto-installed mods, since the user may not know the full details of how to mark them as not auto-installed.

Changes

• Now the Changeset tab list has a "Skip?" column at the right
• Changes that would be simple to remove from the changeset (independent from other changes) have an "X" icon in this column with a tooltip like "Don't Install MyMod 1.0.0"
• Changes that are not simple to remove (other changes depend on them) have no such icon
• If you click an X icon, a confirmation popup asks you if you really want to remove that change from the changeset
• If you cancel in the popup, the change stays in the changeset
• If you confirm the removal, the change is removed and the changeset is recalculated
• A bug is fixed where clicking the Clear button would mark many auto-installed modules as not auto-installed

Thanks to @JonnyOThan for providing in-depth UI feedback and saving us from ambiguous checkboxes.

Fixes #4012.