Merge rectangle and ellipse tool into BasicShapeTool

[#76140044]

Now it supports rectangles, ellipses, circles and squares.
moved BtnGroup into separate file
Merge branch 'colorTool'
Merge branch 'master' of github.com:concord-consortium/drawing-tool

Conflicts:
	app/scripts/ui.js
Merge branch 'master' of github.com:concord-consortium/drawing-tool

Conflicts:
	app/scripts/ui.js