Implement new hotkeys in Filter editor

[Alex-302]

1. Ctrl-/
   • disable/enable a rule in grid mode;
   • comment a rule by ! in the editor mode;
2. Ctrl-D - remove a rule/line from user filter. It must be also applied to selected group of rules.

[contribucious]

:thumbsup: Possible additions:

3. Ctrl-+ - add a rule/line in user filter (i.e. equivalent to clicking on the central Add a rule button or the + bottom icon).
4. Ctrl-N - add a filter (i.e. open the adequate modal window, to add a New filter).

:bulb: The last one is in the continuity of the already existing <Ctrl-E - edit a filter>.