Tabletools and liststyle should not force custom context menu

[Marek Lewandowski]

Currently there's no way to load tabletools/liststyle plugin without adding a custom context menu. This is something that part of community would like to avoid.

Reason for this is that these plugins has a ​hard requirement on it, and this is how we need to proceed, because by default contextmenu is the only way how people can interact with it.

[Marek Lewandowski]

It has been requrested on SO: ​http://stackoverflow.com/questions/2246631/how-to-disable-ckeditor-context-menu

This issue has some story, similar issue was in #9284 however it came with a different result, by simply puting an error.

[Marek Lewandowski]

The solution that might work here is to add:

• optional property to ​CKEDITOR.pluginDefinition, so having plugin listed there it means that it's required, but optoinal.
• Simply go with another configuration option like config.contextmenu_disable and if true contextmenu plugin would be loaded but it's logic wouldn't kick in.
• Extract logic from current plugins to e.g. tablettolsbase, liststylebase (to be consistent with embedbase) and then tabletools would be only about bringing interface for the feature.

[Marek Lewandowski]

For others looking for a workaround the one that comes to my mind is simply... to stub contextmenu plugin.

So if you're building CKEditor using [presets builder](​https://github.com/ckeditor/ckeditor-presets), make your fork where you add a single file to plugins as simple as that:

CKEDITOR.plugins.add( 'contextmenu', {} );

And that's all, then just go and build.sh your distribution.

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For standard, uncompressed ckeditor-dev version, you simply need to replace whole plugin contextmenu plugin dir, leaving only this stub.

That's the workaround needed until this issue is solved.