Add the load of the races respository files.

The main idea here is add some convention to add new content data for races, items, character classes, backgrounds and etc.

I used a little bit of meta programming. XD
I'm planning to extract this behaviour with a little bit more of metaprogramming to a module called repository. The other modules can include the behaviour. Or maybe create more crazy stuff like read the directories and auto define the repositories.

What do you think? @fabioyamate