ContextMenu dynamic item titles

[blickfeld7]

Currently the title is hardcoded on the contextMenu. It would be nice to be able to set the text for the contextMenu programmatically in a method called e.g. setTitle, which receives a context object (like getEnabled and doAction)

https://github.com/xeokit/xeokit-sdk/blob/master/src/extras/ContextMenu/ContextMenu.js#L54

[xeolabs]

Added in 8576910