Draft: Don't unload/remove plugins immediately, instead require a restart to prevent unclean unload/crash

Sometimes unloading a plugin can cause a crash. Change it so that disabling a plugin just marks it as disabled and display a message stating it will be disabled on restart. For removing plugins (which deletes the plugin file), add the plugin file path to a settings entry called plugins_remove and then check this entry when loading a new plugin at startup. If the plugin file is on the remove list, delete the file instead of loading it.

I want to make this behavior configurable with another setting before merging it, but will probably make the default behavior this new behavior at least until we potentially have a more reliable unload/remove system in place.