Rework Currency Symbol Parsing

[JRoy]

• Made currency symbol standardized in Kit
  • Kits should be in a standardized format.
  • Having monetary rewards in kits should not break based off of a config value oriented around currency display (suffix).
  • Additionally, the dollar sign should be the standard money symbol which works on all servers and should not be tied to the server's individual currency symbol.
  • Note that the server's individual currency symbol will still work but probably should not be used due its volatility.
• Reworked config currency symbol parsing in Settings
  • Simplifies the number of actions needed to sanitize the input.
  • Now just defaults to $ if the currency-symbol cannot be parsed.
• Removed symbol-suffixed parsing in NumberUtil#sanitizeCurrencyString

[mdcfe]

Note to self (or others) of things to test before approval:

• All signs that accept currency values (trade, buy, sell etc) - both custom currency symbols and $ are expected to work, and as either prefix/suffix as per the config (given that people may have previously set up signs with custom currency symbols/formatting)
• Money given in kits - $<amount> is expected to work
• All commands that accept a numeric currency amount - custom symbols, no symbol and $ are all expected to work, and as either prefix/suffix depending on config
• Vault formatting method should always return custom currency symbol as either prefix/suffix as per config