OPAL-2118: Chaging trash icon and removing close window icon for filters
Merge pull request #356 from emorency/feature/OPAL-2118-Values-filter

OPAL-2118: Chaging trash icon and removing close window icon for filters
Added some entries in main Administration page
Users administration UI refactored
Code cleaning
Removed plugins item from main administration page
User password are hashed with SHA-256 and salted