Adapt the screenshare processing script to changes to the api for events handling in
the recording-and-playback core libs.

This reverts a bbb-specific customization made in the jquery.acornmediaplayer.js
file: it's restored to what the upstream player did. I can't find any explanation
for why this change was made in the first place? Reverting it doesn't seem to
cause any playback issues (Popcorn still works, in particular).

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.10.3 to 1.10.4.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/master/CHANGELOG.md)
- [Commits](https://github.com/sparklemotion/nokogiri/compare/v1.10.3...v1.10.4

)

Signed-off-by: dependabot[bot] <support@github.com>

Found another case where the html5 client was passing through control
characters, in the original presentation name field.

Rather than play whack-a-mole with different fields which may eventually
get poorly sanitized user data, apply the control character filtering
to all properties.

Adjust the character range to do the following:
* Allow horizontal tab (0x09), it's not problematic.
* Disallow control characters in the range 0x1A-0x1F. Probably missed by accident.

 - use thumbnails to find the num pages of presentation instead of swfs as we now turn off generation of
   swfs for html5

It used to print:

Failed to download file: undefined local variable or method `respose' for BigBlueButton:Module
Did you mean?  response

because the incorrect variable name was used in the error message.

There was no effect other than the message in the log, since the shared notes
couldn't be archived anyways, and the only thing the exception did was ...
prevent the shared notes from being archived.

 - log upload captions params

It now attempts to convert the uploaded caption file to WebVTT and
updates the index file.

Some additional validation/normalization is added for the language tag,
and some cleanup has been done for logging.

Makes testing easier

FFmpeg has pretty good format autodetection even if the filename has the
'.txt' extension, so just rely on that. It'll even pull subtitles out of
video files - although I expect we'll have size limits so that doesn't
happen.

Rather than running the tool in a loop, I'm using inotify to watch for
new files being created (ideally, the other rap workers will be migrated
to this style in the future). The trigger for processing is the creation
of the .json index file for the uploaded track.

This reverts commit 9ad783fa.

We ended up not being able to rename the etherpad nginx file, so this
recording format has to go back to using a different name.

Sometimes when text is pasted into the whiteboard text tool from
external apps, it'll include control characters that mess up later
recording processing scripts.

Run the same cleanup as already used for chat messages on the whiteboard
text as well.

The cleanup has been adjusted to allow newline and tab characters. They
won't really cause issues in chat, and newlines (at a minimum) are
required for the whiteboard.

This is a workaround for #7356