Conform to Americans with Disabilities Act in BOY

[berryma4]

As our policy states, we must meeting regulatory requirements.

The most pressing of the requirements, is to allow a user to 'tab' through widgets; or in general use the keyboard to perform work.

This also happens to be something that most operators prefer anyway. For example, a BOY screen has many sliders, a user would like to tab through them and increase or decrease the value from the keyboard (with also having the ability to change the step size).

[kasemir]

Adding this to BOY is complicated by the mix of SWT widgets - which do support TAB navigation - and Draw2D based shapes, which don't.

The JavaFX-based demo for #1230 allows navigation between widgets. TAB traverses widgets using the order of widgets in the model. This can be controlled by properly arranging the order of widgets, but in reality is simply based on the order in which widgets were added, not useful for navigation.
Lucklily, cursor keys (may have to add SHIFT) navigates based on screen location to the next widget at the 'left', 'right', etc., which is usually what you want.
"Space" on an action button invokes it.

[berryma4]

This has been added to Display Builder