docs/plugins/: Added videobalance and videoflip to the docs.

docs/plugins/: Added videobalance and videoflip to the docs.

Original commit message from CVS:
* docs/plugins/Makefile.am:
* docs/plugins/gst-plugins-good-plugins-docs.sgml:
* docs/plugins/gst-plugins-good-plugins-sections.txt:
* docs/plugins/gst-plugins-good-plugins.hierarchy:
Added videobalance and videoflip to the docs.
* gst/videofilter/Makefile.am:
* gst/videofilter/gstvideobalance.c:
(gst_video_balance_update_tables_planar411),
(gst_video_balance_is_passthrough),
(gst_video_balance_update_properties), (oil_tablelookup_u8),
(gst_video_balance_planar411_ip), (gst_video_balance_set_caps),
(gst_video_balance_transform_ip), (gst_video_balance_base_init),
(gst_video_balance_finalize), (gst_video_balance_class_init),
(gst_video_balance_init), (gst_video_balance_interface_supported),
(gst_video_balance_interface_init),
(gst_video_balance_colorbalance_list_channels),
(gst_video_balance_colorbalance_set_value),
(gst_video_balance_colorbalance_get_value),
(gst_video_balance_colorbalance_init),
(gst_video_balance_set_property), (gst_video_balance_get_property),
(gst_video_balance_get_type), (plugin_init):
* gst/videofilter/gstvideobalance.h:
Ported to 0.10. (Fixes #326160)
Added docs.
* gst/videofilter/gstvideoflip.c:
* gst/videofilter/gstvideoflip.h:
Added docs.