Revert 'presentation' dir to 0.81 code, add 'presentation2' for 0.9

This fixes an issue where recordings copied from a 0.81 server might
not play back correctly on a 0.9 server.

This changes the 0.9 recording scripts to use playback support files
from a different subdirectory, 'presentation2', while existing 0.81
recordings continue to use the 'presentation' directory.

If the raw files from an old recording are reprocessed, it will
switch to using the newer playback support files.
Use the directory presentation/0.9.0 instead of presentation2

This makes it a bit more obvious how the versioning can work going
forwards, and makes it so that we do not need to update the nginx
config each time we have a new version of the playback files.

The 0.81 files remain at the top level of the presentation directory
for compatibility reasons.
Move 0.81 files to a subdir, add nginx redirect for them.

Now the 0.81 presentation playback files are in an appropriate versioned
directory. If desired, the recording metadata can be updated to reference
the versioned files directly, but an nginx redirect has been added so
that unmodified recordings will also work.
Add a note to the nginx config to tell 0.9.0 beta users of a possible upgrade path
changed webrtc error messages to errorcodes, fixed a bug with webrtc call failing at echo test
Merge pull request #407 from SenecaCDOT-BigBlueButton/more-webrtc-fixes

WebRTC fixes
 - cleanup
 - fix txt uri for accessibility
 - start implementing auto start recording
 - fix https://code.google.com/p/bigbluebutton/issues/detail?id=1776
 - allow start/stop recording when doing autostarting recording
 - follow redirects when downloading presentation
 - modify lib path
Merge pull request #409 from SenecaCDOT-BigBlueButton/bigbluebutton-client-system-check-app

initial commit for client check app
Merge branch 'master' into follow-download-url-redirect
initial commit for client check app
adding gitignore, removing files that are not required
clearing more files that are not required and additional paramaters to gitignore
modifying build.xml to copy custom BBBClientCheck.html file, adding additional value to gitignore
 - don't let viewers mute/unmute others through the webcam window