New recipes: libnice.recipe, libnice-static.recipe

Also add to the gstreamer-1.0-net package
gstreamer-1.0-core.package: Don't add the plugins_core and lang categories for -bad twice

Was causing a build failure:
https://ci.gstreamer.net/job/cerbero-fedora-20/1476/consoleFull
libnice,-static.recipe: Don't pull in gtk-doc

gtk-doc-lite will give us the macros, which is all we need on platform != LINUX.
For Linux, it's pulled in by bootstrap. Compiling gtk-doc on other platforms
causes a build failure:

https://ci.gstreamer.net/job/cerbero-ios-universal-7.1/1219/console
New recipe: icu.recipe

Cross-compilation is complicated, so has been left alone for now
harfbuzz.recipe: Now that we have ICU, we can actually build with ICU support
New recipe: libsusrsctp.recipe
New recipe: gnome-js-common.recipe
New recipe: javascriptcoregtk.recipe

Lots of hacks to build only JSC and not WebKit-GTK+
More hacks to cross-compile on Android
New recipe: seed.recipe
New recipe: openwebrtc-gst-plugins.recipe
New recipe: openwebrtc.recipe