Set the default elevation reference for swapping pressure network parts

[Drea_Mueller]

When editing pressure networks and swapping parts is required, the default elevation reference is set to Top of Pipe.  99% of the time when swapping a pressure part, I want to hold the Centerline.  There should be a way to set the default elevation reference when swapping pressure network parts in the SwapPRessureNetworksParts command reference.  If this its not something that can be added to the command reference, I would strongly suggest setting the default toggle to be Centerline as it is overwhelmingly the elevation that needs to be held. 

@chriscowgill7373

@swalz 

[chriscowgill7373]

I think it holds outside top by default, because when you layout a pressure network it uses the top outside of the pipe to place it in the profile.   I dont disagree that it would be nice to have an option, because it should be flexible and if you use a setting enough it should be able to be set as a default.