update packing logics to honor activities and tabs

at the same time using MaximizeArea instead MoveArea

ratio:
movearea allows to pack windows under panels and while
one can expect users of packing to know alt+lmb, we usually
do not allow to loose the titlebar

Moreover this relies on packing against dock windows what
fails with "virtual" struts as input shaping panels
(eg. cairo-dock?) might use (ie. we we would also have packed
against plasma panel shadows - back then ;-)

BUG: 180084
REVIEW: 111603
FIXED-IN: 4.11