image_calc: Use output_calc.tif rather than output_union.tif, other minor
image_calc: Use output_calc.tif rather than output_union.tif, other minor

njwilson23/StereoPipeline,NeoGeographyToolkit/StereoPipeline,DougFirErickson/StereoPipeline,ScottMcMichael/StereoPipeline,ScottMcMichael/StereoPipeline,DougFirErickson/StereoPipeline,aaronknister/StereoPipeline,oleg-alexandrov/StereoPipeline,NeoGeographyToolkit/StereoPipeline,ScottMcMichael/StereoPipeline,njwilson23/StereoPipeline,aaronknister/StereoPipeline,NeoGeographyToolkit/StereoPipeline,oleg-alexandrov/StereoPipeline,NeoGeographyToolkit/StereoPipeline,ScottMcMichael/StereoPipeline,NeoGeographyToolkit/StereoPipeline,ScottMcMichael/StereoPipeline,DougFirErickson/StereoPipeline,ScottMcMichael/StereoPipeline,oleg-alexandrov/StereoPipeline,DougFirErickson/StereoPipeline,DougFirErickson/StereoPipeline,oleg-alexandrov/StereoPipeline,njwilson23/StereoPipeline,njwilson23/StereoPipeline,DougFirErickson/StereoPipeline,NeoGeographyToolkit/StereoPipeline,aaronknister/StereoPipeline,oleg-alexandrov/StereoPipeline,aaronknister/StereoPipeline,njwilson23/StereoPipeline,oleg-alexandrov/StereoPipeline,njwilson23/StereoPipeline,aaronknister/StereoPipeline