Merge pull request #592 from liuchuangww/user

Add password validator
Fixed user icon
Merge pull request #593 from adivspan/user-adivspan

Fixed user icon
Fix for getUserModel
User module bug fixed
Fixed bug that avatar cannot be displayed
Merge pull request #594 from sexnothing/user

User module bug fixed
Added private message link
Fixed ie css bug and icon html
Merge pull request #596 from adivspan/user-adivspan

Fixed ie css bug and icon html
Refactored user resource loader
Merge branch 'user' of https://github.com/pi-engine/pi into user
Merge pull request #595 from linzongshu/user

Fixed bug that avatar cannot be displayed
Remove user-role link after deletion of a role
Add user validator