manual spelling
Update 11_working-with-plugins.html
Fix broken link. Add meaningful link text.
spelling
New middle click description plus corrections

* Fix Button numbers for mouse
* Add section on Middle Clicking
* Instructions for Mac OS right click
* General copy edits
Add contextual links
Scroll Wheel
copy edits
initial version of videotimeline doc..
fix image URL
Merge branch 'patch-1' of git://github.com/dbolton/manual
fix typos and clarify video-integration.
some clean-up of the video-operations doc
more tweaks to the video-manual
add note about supported codecs
reorganize transcoding/format/codec page
insert missing verb
fix link to ffmpeg.org
update video-export doc, move "video export info" dialog to manual