Created IDWInterpolation operation.

- Moved SpatialIndex to geotrellis.feature
Made WebRunner more configurable.
Merge remote-tracking branch 'lossyrob/op/IDW' into webrunner
Made endpoint prefix configurable
Added .interesects method to Extent
Specify where to get jai_core explicitly
Merge pull request #558 from lossyrob/build/jai

Specify where to get jai_core explicitly
Merge pull request #556 from lossyrob/op/IDW

Created IDWInterpolation operation.
Removed catalog path from reference.conf

This really gets in the way when you are trying to deploy GeoTrellis apps that do not actually use a catalog.
Also, in admin, notify the user if the catalog is empty.
Merge pull request #557 from lossyrob/webrunner

Made WebRunner more configurable.
Remove debug code
Merge pull request #560 from lossyrob/bugfix/shortestpath

Remove debug code
Merge pull request #559 from lossyrob/nocatalog

Removed catalog path from reference.conf