[UC6] Add breakpoint from menu

[Mykola Baranov]

Description: Add opportunity to add breakpoint from menu to line where is cursor is now. To implement this, please, add new QAction to "Debug" menu - "Toglge Breakpoint" with shortcut - F9

Basic Flow:

1. User clicked under "Toggle Breakpoint" in "Debug" menu.
2. Add breakpoints to line, where cursor is now

Alternative Flows:
2a. Cursor position is undefined.

• 2a1. Don't toggle breakpoint/
• 2a2. Show message with error - "Breakpoint cannot be added unless you set cursor poisition".