Added el_GR locale

Also provides some extras for the greek locale, eg. male and female names, latitude()/longitude() return coordinates that fall inside a (crude, 4-sides only atm) polygon encompassing Greece.

Borrows some names from [fzaninotto/Faker/el_GR](https://github.com/fzaninotto/Faker/blob/master/src/Faker/Provider/el_GR/Person.php).