Added functions for set/get global lock. New scheme with undo in fast collaboration were moved to standard shortcut Ctrl+Z.

Feature/mobile web

Fixed issue in commutation of different content changes. Also fixed bug that new reversed changes weren't add to list of all changes.

Fixed bug with adding a new paragraphs in the main document. Fixed bug with loading reversed changes for client who made this changes. Added a test hotkey for Undo in fast collaborative.