Breaking: Upgrade MediaElement.js (fixes #298)

[swashbuck]

Fix #298

🚧 Work in progress 🚧

Breaking

• Upgrades MediaElement.js from v2.21.2 to v7.0.5. This includes breaking namespace changes.
• Removes Flash support
• Removes IE 9/10 support
• Removes Vimeo support (Vimeo-specific styles and JS shims). Anyone who needs Vimeo support should migrate to the Adapt Vimeo plugin.
• TBD

Notable changes and deletions

• First off, refer to the MediaElement migration notes, particularly regarding the namespace changes.
• speed, jumpforward and skipback have moved to mejs plugins. Other plugins can be considered for inclusion in the future.
• Removed buildfullscreen() override ("Overwrite mediaelement-and-player buildfullscreen to remove global delete"). The only significant difference in the current override was to remove two delete hideTimeout lines. The new buildfullscreen() in mediaelement-and-player.js does not use this.
• The MediaFeatures object is now just Features
• MediaElement success callback passes different parameters: media, node, and instance. I've added documentation about this to onPlayerReady() which is the success callback function.
• Some properties have moved. mediaElement.player changed to mediaElement.options. selectedTrack has moved to the instance object mentioned above.
• Removed killContextMenuTimer override to "remove global delete" since it no longer exists in mejs
• Removed many assets. Icon implementation now uses an SVG symbols.

Configuration changes to existing courses

None

Dependencies

Requires Vanilla theme updates from adaptlearning/adapt-contrib-vanilla#524 Vanilla version TBD.