Allow passwords longer than 11 characters

It is poor security practice to set a maximum length on a password, especially one as low at 11 characters. I kept the minimum at 4 characters just to not break backwards compatibility, but it should really be a minimum of 8 characters these days.
Revert "Check for empty identity_columns after array_diff"

This reverts commit f145deefbc315aaf833ed3d72bf8cab895996f69.
Passing nonexistent credentials should return null

Fixed #215
Fix for validation bug on password change
Tiny changes
Russian translation
Merge pull request #220 from AfzalivE/master

Passing non-existent credentials should return null user. Thanks @AfzalivE
Merge pull request #218 from mfjordvald/patch-1

Allow passwords longer than 11 characters. I agree @mfjordvald
Merge pull request #223 from Wyorma/bugfix

Fix for validation bug on password change. Thanks @Wyorma
Merge pull request #224 from Wyorma/rulang

Russian translation. Thanks @Wyorma