Break up the installation notes a bit
Break up the installation notes a bit

I find it silly for people to download the whole entire USGS mission
support data. The docs now reflect downloading base at bare minimium
and then downloading specific missions.

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