Provide a Tiny editor button for Opencast

[abias]

Note: This issue is just located here in tool_opencast as placeholder. It will be moved to a Github repo of its own as soon as the project is agreed and started.

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Currently, if a teacher wants to add an Opencast video into a Moodle text, he has to use the combination of filter_opencast and repository_opencast.
However, this process requires patience and expert knowledge:

(note that on a default installation of Opencast even the video thumbnails are broken)

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Let think this process from scratch.
How about implementing a Tiny button:

which will then ask the teacher what he wants to do:

(This screenshot / widget is from MEDIAL)