Increase year to 2013
Merge pull request #2102 from WouterJ/bump_year

Increase year to 2013
Fix small typo in book/validation.rst
fixed explanations about how access control rules work
Furthering @fabpot's changes to the access_control explanations in the security chapter
Merge branch '2.0' into 2.1

* 2.0:
  Furthering @fabpot's changes to the access_control explanations in the security chapter
  fixed explanations about how access control rules work
  Fix small typo in book/validation.rst
  Increase year to 2013