fix bug #30 and add support for MultiLineString

1) PositionsAdapter.parsePositions() recognizes the position in the array (within the recursion of the method)
thus it is possible to remove the workaround for bug # 15 in GeometryAdapterFactory.buildPolygon() and GeometryAdapterFactory.buildMultiPolygon()
2) GeometryAdapterFactory: buildMultiLineString() added and used in buildGeometry()
also added test for MultiLineString containing just a single LineString
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