Get rid of Currency Lists in the code base

[PostScripton]

I've decided to get rid of Currency Lists because of their overwhelming compelexity in the realisation. It would be simplier to set a Currency List only in the config file but not in the code.

It doesn't meant to get rid of it entirely but of it from the methods such as:

• Currency::currentList()
• Currency::setCurrencyList()
• Currency::isIncorrectList()
  and of the constants:
• LIST_ALL
• LIST_POPULAR
• LIST_CUSTOM
• LIST_CONFIG
• LISTS

[PostScripton]

Done here: #90