Force windows to maximize on open

[Séamas Ó Brógáin]

I spoke too soon. My windows continue to misbehave (Unity 2D). Libre
Office appears to be the worst offender: if I turn my back on it for a
few moments to look at something else, especially if I use the keyboard
shortcut to navigate between open applications, it has usually jumped
back to maximum size. Firefox continues to do the same; other
applications seem to be behaving themselves. Infuriating!