Bug: update user page design

[bazilval]

Summary

The page looks like this now:

I suggest to make closer to the design I made for domains, it looks lighter:

• remove gray buttons, replace them with light ones,
• make the input line and the add button in one line,
• align pagination in the center of the table,
• correct how arrows are displayed on sorting buttons (an arrow should be displayed only on the active sorting property)