Add property to change dgs selector behavior

[Fernando-A-Rocha]

I'm a fan of the DGS Selector. It would be nice to have the following behavior (can be enabled via a dgs-dxselector property):

• clicking right arrow when the last item is selected => selects the first item instead of doing nothing
• clicking left arrow when the first item is selected => selects the last item instead of doing nothing
• same behavior for scrolling with mouse up/down ontop of the slider

[Fernando-A-Rocha]

To implement this, we just need to change:

• onClientMouseTriggered in client.lua
• dgsOnMouseScrollAction["dgs-dxselector"] in selector.lua

Then add an additional property like enableInfiniteSelect or something.