Paint: improve discoverability of paint brush stroke modes

The PAINT EDITOR has some simple tools that are not apparent just by looking at the paint Toolbar.

In particular, the LINE stroke mode is useful, but not obvious. If Blender devs want to increase discoverability and ease of use , these modes should be made more accessible.

Now that the 3dView Edit mode has paved the way, putting related modes 'under the little triangle' of a tool is a UI consistent way to cue Blender users that there're other options available. I propose that Line, Curve, Airbrush, Dots, Drag Dots, Space, and Anchored ALL be made available 'under' the DRAW icon, so that users are clued into their existence.

(I also suggest they be presented in that order, as I imagine that's in order of usefulness/popularity -- menus with the most common choice at the bottom are a PITA. --Or make the order user definable.)