Renamed 'run_addon()' and 'delete_addon', and extended 'delete_addons()' to work on multiple selected addons. Renamed some other local variables. Removed the install button tooltips. Customized the messages displayed when deleting addons based on how many the user was deleting. Fixed the path sent from the QListView for the multiplayer mods. Replaced 'os.mkdir()' with 'os.makedirs()' in 'install_addon()' so we don't get an error if the mods folder doesn't exist.