Add CascadeActiveAppWindows refinements

[rudifa]

This PR proposes refinements to the command cascadeActiveApp (published in rectangle v0.69 from PR #1146 and #1163)

• before: the cascade goes to the top left quadrant

• now: the cascade goes to the quadrant in which the center of the active window is found, so that the user can have up to 4 different apps cascaded

• before: the size of the active (first) window is enforced onto the other windows in the cascade

• now: same, but the size width and height are constrained so that all cascaded windows remain within the screen

[rudifa]

Example screenshot:

[rxhanson]

Thanks for continuing to improve your work here! I understand the changes you're making, and this corner of the code is mainly only touched by you, but if you don't mind let's make the names of everything more readable. I'll comment inline.

[rudifa]

@rxhanson Thank you for the suggestions to make the code more readable, which I now applied.

[rxhanson]

Looks good!

[rudifa]

Thank you!