Add "Password policy" module

#3258 

![screenshot_7_10_13_11_16_am](https://f.cloud.github.com/assets/125707/773470/5b90fa52-e93a-11e2-8bc1-5021823de95d.jpg)

Note, that doesn't if the user can register without email approval, but anyway I don't this this is OS's case.