Since we don't maintain two different shells anymore, there
is no need to maintain the two different sets of categories
in the desktop files.
This commit also drops the "#ifdef CC_ENABLE_ALT_CATEGORIES"
blocks, since the previous commit removed that define.
https://bugzilla.gnome.org/show_bug.cgi?id=790923
Following the previous patch, this patch adds the new alternative
categories to the panels' Desktop files. These alternative categories
are only relevant for the alternative Shell, and do not break the
current Shell in any way.
https://bugzilla.gnome.org/show_bug.cgi?id=767301
Very few of the panel comments provide information that is very
useful. Update them to supplement the panel descriptions - this
will make the search results more helpful.
https://bugzilla.gnome.org/show_bug.cgi?id=694110
