Replace Geotools GeoJSON with thirdpartyutils codec in soql-reference

Happy side effect of removing the reference to geotools-geojson: soql-reference now pulls in about 40% fewer dependency jars :smiley: 
We should really upgrade to SBT 0.13, then you can use the much prettier macro syntax:

    resolvers ++= oldRojomaJsonRepo(scalaVersion.value)