HC: use symbolic style icons

- don't remove the icon theme yet, keep it for gtk2

https://bugzilla.gnome.org/show_bug.cgi?id=732521
Remove gnome-documents high contrast icons

These are distributed by the app itself, and we are going to use
symbolics for these anyway.

https://bugzilla.gnome.org/show_bug.cgi?id=737992
Adwaita: use -gtk-icon-source: none on paned...

...to get rid of the handle decoration istead of setting a transparent
background and abuse a background image for the background color.
Revert "Adwaita: use -gtk-icon-source: none on paned..."

This reverts commit aceabd4f8016a72d2495b9a3f635bb17e08eedd7.
Since this doesn't make sense, it's just picking the wrong terminal
window...
Added Kazakh translation
HC: move to gtk
gtk2 HC: anaconda > liveinst
create-highcontrast: update usage message

gnome-icon-theme-symbolic is no more

https://bugzilla.gnome.org/show_bug.cgi?id=740444
create-highcontrast: process only symbolic icons

Since the switch from gnome-icon-theme-symbolic to adwaita-icon-theme,
this tool has been inadvertently processing non-symbolic icons.

https://bugzilla.gnome.org/show_bug.cgi?id=740444
add gtk2 HC icons

- based on current adwaita-icon-theme and apps-symbolic
Remove a reference to themes/Adwaita/gtk-2.0/Makefile
don't include themes/Adwaita/gtk-2.0 as a subdir
Revert "add gtk2 HC icons"

This reverts commit bfe89c36bd40777767899e1d55f0408a2e6bee05.
Revert "Remove a reference to themes/Adwaita/gtk-2.0/Makefile"

This reverts commit ce6254d0887ecced53344cbabb45159832e91369.
Revert "don't include themes/Adwaita/gtk-2.0 as a subdir"

This reverts commit 916d868dc95639c772a32a693546bb3e4e138fa4.
add gtk2 HC icons

- this time without removing the gtk2 theme, d'oh
prepare for 3.15.2
remove some HC icons that are already shipped with apps
prepare for 3.15.2.1
HC: remove one more duplicate app icon