[geotk] Geotk build upgrated to Maven 3

[Martin Desruisseaux]

Hello all

The Geotk build configuration has been upgrated from Maven 2 to Maven 3. As a 
side effect of this migration, those who use snapshots need to change the 
dependency version number from "SNAPSHOT" to "3.x-SNAPSHOT", because Maven 3 
requires the last form. Those who use releases don't have anything to change.

Note that this migration has no effect on Maven 2 projects that use Geotk; you 
can continue to use Maven 2.

Regards,

     Martin