Add "Play Media" operation.

[anthony-arnold]

This pull request is an answer to Operation Request 246 (play audio.) It adds a new operation, "Play Media" under a new Media category.

The Play Media operation is a lot like Render Image in that it takes raw, hex, or base64 encoded data and outputs a byte array. The present function takes the byte array and produces a base64 data URI. This URI is then fed as the src attribute of either an <audio> or <video> HTML element for rendering.

The type of element is determined based on the MIME type of the incoming data. It must be a valid type beginning with either 'audio' or 'video' (e.g. 'audio/x-wav' or 'video/ogg'.) The MIME type is also used to populate the type attribute of the media element.

The ultimate result will depend on what the user's browser supports. Most common audio and video files should play in a modern browser. A fallback paragraph is rendered in case the user's browser can't support the media type.

The new operation is placed under a new category, "Multimedia". The existing Render Image operation has been moved there.

[anthony-arnold]

I have noted #357 but it appears there's an outstanding issue with that PR.

[anthony-arnold]

Note the Issue this relates to is #264.

[n1474335]

Perfect. Thanks very much for this one.

I made a couple of very small modifications. The main thing was changing the 'Multimedia' category to 'Forensics'. I realise this doesn't seem to fit quite as well, but I'm working on some more comprehensive forensics operations in #440 and I'd rather not have too many categories. It fits here well enough. I would expect most people to find it by using the search box anyway, so I've added a few tags to the description to make that easier.

Thanks once again, this will be really useful.