Add Command Line Interface (REPL) for simple convertions.

A simple main class with a REPL that can be used from command line when starting
the application. The 'convert' command, shortened to 'c', is used with one
argument, which is a number in roman or arabic form. The program detects its
type and converts it to the other form. Double arabic inputs are floored and
casted to integers. Smallcase romans are upcased, this makes the coverter case
INsensitive.

At the moment 4 commands are available:

 - 'exit' to exit the repl and terminate the execution

 - 'help' to display the 4 commands

 - 'info' to display program version, date, author contact, website, licence and
   link to source files

 - 'c' or 'conv' or 'convert' followed by a number.

Usage examples:

 - 'c 42' returns 'XLII'

 - 'c 2.71828' return 'II'

 - 'c MMXIV' returns '2014'

 - 'c xvi' returns '16'