[inkscape-quartz] add gtk-themes support

[su_v]

Follow-up to
Bug #738973 “Issues with inkscape-quartz blueprint”

Related branch:
<https://code.launchpad.net/~inkscape.dev/inkscape/dev-osx>

Related upstream module:
<https://live.gnome.org/GTK+/OSX/Bundling>

1) Include gtk theme engines, themes and a default basic gtkrc into the app bundle
2) Optionally include modified themes to support a limited set of system appearance settings (similar to current app)
3) Possibly add a tool (or internal support) to change gtk theme used for the bundled app
   (e.g. to switch between a light-grey osx-like theme and a dark theme like GIMP on OS X)

[su_v (suv-lp)]

Note: I have basic theme support working in local packages, and will attach a proposal (patch) later this week.

[su_v (suv-lp)]

> basic theme support working in local packages

Example screenshot from package built on 2012-08-29:
<http://dl.dropbox.com/u/65084033/irc/inkscape-trunk-quartz-osx-app-with-mac-menu-and-symbolic-icons-1.png>
using latest Adwaita GTK2 (from gnome-themes-standard 3.5.90.1) with GTK+ 2.24.11, and the new inkscape-symbolic icons currently being worked on by the gnome design team.

[su_v (suv-lp)]

Closing - out-of-date.