Open properties dialog when double clicking on objects

[fredck]

The relative dialog should open when double clicking on objects like images, anchors, flash, form buttons or even tables (in the border... IE only I guess).

[arczi]

This is only an idea + working example. Is it good way?

[fredck]

The idea is good. But of course, the patch is still quite incomplete, as we need to enable it for all kinds of objects we support.

[alfonsoml]

I like the idea, but it will give an error if the contextMenu plugin isn't available.

[alfonsoml]

With my previous comment I just expected to protect the reading of editor.contextMenu._.listeners because that solution was clever and didn't mean extra work.

This new patch means that it's possible to use this feature even if the contextmenu plugin is removed, but I'm not sure if it's worth the extra work. I would like to hear the opinions from someone else.

A benefit of this approach is that there won't be problems if any extra context menu is added.

[garry.yao]

The behavior on 'dbclick' should be distinguished from which on 'contextmenu', e.g. 635_2.patch opens table dialog when double clicking inside cell, which is wrong.
Beside, the detection mechanism should be simplified, where dialog should simply declare a listener of one param - element, and it would be better the 'wysiwyg' plugin's responsibility to hold such listeners instead of 'dialog' plugiin.