Grid numbers

[davidbau]

premr suggested: Allow numbers on the grids so people can know where to move the turtle in x,y rather than just relative movements

davidbau wrote: Yes great idea - there should be a debugging button that toggles "show movement labels" that

(1) shows grid labels that prem suggests and
(2) puts a protractor / compass rose under the current position of the
turtle
(3) shows a forward /back number line under the current position of the
turtle.

And maybe when in this mode, mousing to different parts of the screen
should preview code like "moveto 42, 32" or "fd 108" or "rt 144". Some
sort of click or gesture should enter that code into the editor.

Originally PencilCode/jquery-turtle#20

[davidbau]

The protractor is implemented! The UI solution was a clickable "tooltip" in the corner that tells you zero-centered coordinates.