Fixing the following warning when generating documentation:
xml/element-chromium.xml:74: element refsect2: validity error :
ID GstChromium already defined
<refsect2 id="GstChromium" role="typedef">
^
Warning: multiple "IDs" for constraint linkend: GstChromium.
DOC Fixing cross-references
Adds the new 'gaudieffects' plugin, originally found
here: http://github.com/luisbg/gaudi_effects
Contains the following video effect elements: burn, chromium, dilate,
dodge, exclusion and solarize.
Thanks to Jan Schmidt for the reviewing and refactoring