Use different icon for left-click context menu

[asvishnyakov]

In menu branch, and especially after implementing #292 we must change icon for left-click context menu. My proposal is ... (three dots) symbol, it's used for same thing in Azure design. Also, we may place it on right side, instead of left

[asvishnyakov]

Changing of this icon will cause avalanche effect on platform and module versioning which must be synchronized. Now we use "fa fa-ellipsis-v" class explicitly. If we will change it to neutral class like "cntxt-menu-ico" our modules will be incompatible with old platform versions, so they will have to require platform version with this css class support. Possible, the same effect will be caused by other UI changes where modules code affected. So I will prefer to synchronize all of this UI updates.