DUI: new styling update

# Preface
After last EB's review he found a lot of small, but really important things.
I have decided to combine them in one PR.
# Tasks
[MAGN-4661](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-4661) DUI: The background color of library has to be #343434
[MAGN-4666](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-4666) DUI: Get rid of this margin
[MAGN-4667](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-4667) DUI: Text labels for classes are should not be vertically centered
[MAGN-4668](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-4668) DUI: The margins for collapsed icon are off
[MAGN-4670](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-4670) DUI: The margins for class icons are off
[MAGN-4671](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-4671) DUI: Create, actions, query labels to have styling and padding
[MAGN-4664](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-4664) DUI: When a library category is open, the category bar should have same hover over effect as the collapsed state
[MAGN-4677](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-4677) DUI: Changes to the search bar in library

# Reviewers
@Benglin,@vmoyseenko, please take a look.

P.S. today I'm too lazy to make printscreens...