change "UMD" to "UMD/Google"

per Google's request
Add Google

Changed "University of Maryland" to "University of Maryland/Google"
added Google's name to loss, gain, and extent

Added Google's name to references to loss, gain, and extent layers per Google's request
Merge pull request #831 from alyssaw/patch-65

added Google's name to loss, gain, and extent
Merge pull request #830 from alyssaw/patch-64

Add Google
Merge pull request #829 from alyssaw/patch-63

change "UMD" to "UMD/Google"
Merge branch 'master' of github.com:Vizzuality/gfw into staging