ArenaFighter

Fixes the following bugs

• [wager] showing up incorrectly when getting a command usage prompt
• Stop fighters betting on themselves
• Prevent players from stopping the arena teleport by sitting or sleeping
• Stop fighters from dropping items during fights to dupe items
• /bet not checking for economy methods loaded and returning an internal error when ran
• Essentials method calling its self even when not loaded causing plugin loading errors

Adds

• Keep inventory for fighters
• Support for old ZCore economy officially
• Automatic version pulling for /fightabout command