Add virtual universe output filter

We need a virtual universe output filter. The non-virtual one should persist within the node selection menu as it allows outputting to channels that do not belong to a patched fixture. The following things need to be supported / done:

• Implement a virtual output filter that accepts the selection of a patched fixture within its configuration dialog.
• Allow the selection of which channels should receive direct output or which channels should accept a constant value or should not be updated at all
• For every selected channel that should receive direct input create an input port of the associated data type. For example a set of RGBW channels should only provide one input port of type color.
• Within the configuration menu of the virtual filter one should be able to select defaults for the channels that are selected to be updated with a constant value.
• During filter instantiation of the virtual filter, it should also instantiate the the required conversion filters and constants
• Changing the channel of a patched fixture should be honored by this v-filter. (If the filter only queries the start universe and channel of the fixture during instantiation of filters, this should be done automatically)
• The automatic filter generation of fixtures should be updated to use this filter instead.