fix #1 - add support for GeometryCollection

including tests
parts (especially GeometryCollectionCodec and JtsGeometryCollectionIterable) based on pull request #24 from lurajon
Merge branch 'multiGeometryFullSupport' into geometryCollection

Conflicts:
	core/src/main/java/com/github/filosganga/geogson/gson/GeometryAdapterFactory.java
	core/src/test/java/com/github/filosganga/geogson/gson/GeometryAdapterFactoryTest.java
clean up after merge of branch multiGeometryFullSupport (pull request #31):
fixed GeometryAdapterFactory
enhanced tests

added missing GeometryCollection
Merge pull request #33 from bkiselka/geometryCollection

fix issue #1 : add support for GeometryCollection