Settings: check if the icon choser app give valid content back

due that a lot weird filemanager exists which show up in the action
choser to be able to crop even if they do not (and a lot famous
one do that as well) check if the file which returns exists and
if it has content at all. Otherwise inform the user that
the chosen app does not support this action

Change-Id: I66524c4b07714944bea4d3e264d918d0b8b662ff
Settings: slightly adjust PIE default values

to fit frameworks base change

Change-Id: If213abd25744472c5d2f93a2b146dae6c12f4017
Settings: dslv do not allow to add recent, home, back main action twice

to have it twice causes problems on navbar pie and wherever in future
home, back, recents is used when the system disables this buttons and
more then one per feature exists. Due that a user do not set eg
2 home buttons on navbar let us block it and give the user a hint
that this is not allowed. All other actions can be added twice

Change-Id: I729d166139403e65b948f45acf36a47b7de7eb4c
Settings: remove always transparency mode navbar/statusbar 1/2

problem is that the transparency on most app totally break due
that a lot apps do not draw behind navbar and statusbar. Nearly
all user never use always mode and just use it on launcher
and lockcreen. So let us remove it

as well a bit cleanup in arrays and strings

Change-Id: Ic6d65d96a6665071689f3bc607c11aeadd29d8b8