Add support for other currencies

[SrGMC]

As stated in the title, it would be nice to have support for other currencies, such as Euros, where the currency symbol is suffixed instead of prefixed, or Pounds, where the symbol is prefixed like Dollars.
The app can only use one currency, an this could be set in a variable on a configuration file.

Also, thousands and decimal separators in Europe are switched. 1,299.98 in US is 1.299,98 in Europe. To simplify things, another configuration variable could be used to disable thousands separator so the decimal separator is the same (a .) which is common in programming languages ans computers.

[inoda]

I'd be happy to accept a PR for this!

[mzygadlo]

Hi! I created a PR for this issue #96