wrappercamerabinsrc: Unref elements after usage

gst_bin_get_by_name() and gst_bin_get_by_interface() both return
references to elements that need to be unreferenced after usage.

https://bugzilla.gnome.org/show_bug.cgi?id=734524
docs: remove eglglessink from docs as it no longer exists
opengl: update element docs for 1.x
docs: remove rtpvp8 plugin docs, the elements are now in -good
docs: update for git master
examples/gl: unref bus and element after usage

gst_pipeline_get_bus() and gst_bin_get_by_interface() both
return references that need to be unreferenced after usage.

https://bugzilla.gnome.org/show_bug.cgi?id=734527
opusenc: Unref pad template caps after usage

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=734517