Move templates

Well, this one is the more tricky! ;)

Move all templates to ajax_select/ directory inside templates/ in order not to pollute toplevel templates directory.
This is a strict convention in Django world, and imho it's better to fix this sooner than later.
With a clear warning, people can update their templates before updating ajax_select, and at least one can make symlinks if he prefers to keep this unconventional situation on his repo.

What do you think of this change?

Yohan