Opticks-1577:adding configuration entries for setting backgrounds transparent for pngs and geotiffs

git-svn-id: svn://svn.code.sf.net/p/opticks/code/trunk/future@18691 6d0fddd1-9640-0410-91f9-aa98d5e64d34
Opticks-1577:adding configuration entries for setting backgrounds transparent for pngs and geotiffs

git-svn-id: svn://svn.code.sf.net/p/opticks/code/trunk/future@18692 6d0fddd1-9640-0410-91f9-aa98d5e64d34
Added .gitignore files to match svnignore properties