Externalizing and improving search configuration

I remember reading somewhere here that you wanted to start modularizing the configs sections on vimrc, so I just did that with the search related ones, and added a new config to make searching better (imo, of course :smile: ). 

Now:
   * if you wanna search for `doStuff` you can search for `dos` and have it found
   * if you wanna search for `doStuff` but not wasting the time with occurences like `dos is crap` then you can type `doS` and only match the exact occurences...

Quite handy imo.
Thanks