Remove secondary icon for brushes

[Viza74]

I regret to inform you about this very serious bug. All the other tools in the left toolbar have a tooltip except the brush tool. It is pretty sad.

Is there a more serious category for bugs than a "crash" bug? Because this issue is definitely that.

;)

[nurpax]

:) I dropped it because it messed up with the sub-tool selector.

But @Esshahn opined that maybe the sub-tool menu is sort of redundant anyway as the brush selection can be cleared with ESC. Or maybe first click on the brush menu would enable brush paint mode if there's a brush selected and another click would clear the brush and go into brush selection mode.

[Esshahn]

(issue renamed for clarity)

• remove the secondary (mousedown) icon from the tools menu as ESC handles that now
• add tooltip to primary icon