Added upgrade shortname to translation callback

This way the same callback can be used to translate multiple upgrades
registered by the same plugin.
Fix upgrade ordering in README
Push some debugging code for experience settings

This was used to balance the experience settings and might prove useful
for somebody as well..
Added list of rpg commands to rpgmenu

Plugins can register their rpg commands with the core and have them
displayed in the menu next to the default ones.