Tells you which preset you have chosen via shortcut

After changing brush using shortcuts "Next Favorite Preset", "Previous Favorite Preset" and "Switch to Previous Preset" (by default binded to keys: " , ", " . " and " / ") it might be not obvious, which preset just have been selected.

This patch makes so, that after selecting another preset using one of theese shortcuts, selected preset's name and thumbnail will be shown in floating message.

Differential Revision: https://phabricator.kde.org/D7454
GUI: