Plugins: Add plugin settings

- Add support for plugin settings, they appear in the same menu as the plugins, indented from the left to emphasize which plugin the setting belongs to
  - Note that plugin settings can still be changed even when the plugins are stopped
- Add tooltips to plugin menu to view the plugin descriptions, description_lang can also be used
- Fix scolling not working on song select when returning from game settings
- Let instance owners set default plugin files in config.py, to make them easier to maintain
- plugins.add() can now add plugins using a url
- Plugins can be hidden from the plugin menu using PluginLoader.hide, an option in plugins.add(), or in config.py
- Make p2.disable() incremental so that multiple plugins can disable multiplayer independently
- Server no longer crashes if certain optional config fields were not copied over from an updated example config
- Fix not being able to unload plugins if one was imported with errors

public/src/js/importsongs.js

@@ -108,7 +108,10 @@
 					)
 				))){
 					this.plugins.forEach(obj => {
-						var plugin = plugins.add(obj.data, obj.name)
+						var plugin = plugins.add(obj.data, {
+							name: obj.name,
+							raw: true
+						})
 						if(plugin){
 							pluginAmount++
 							plugin.imported = true