Suggestion: add a devtools folder

[ehennestad]

Hi,

I am proposing to create a devtools folder in the root directory of a toolbox. This folder could include buildUtilities, tests, reports, ToolboxPackaging.prj, buildfile.m etc.

I find that the root directory can become a bit crowded following the guidelines, and on GitHub it is very nice to see the README without scrolling a long way.