Add RegisteredLayerType and register initial layer types

To help support Spatial Cypher project, allow for mapping of String
to GeometryEncoder and Layer classes for streamlined Layer creation.
Add WKT RegisteredLayerType
Start moving towards new config api
Merge remote-tracking branch 'origin/master' into johnymontana

Conflicts:
	src/main/java/org/neo4j/gis/spatial/SpatialDatabaseService.java
Improved read-only transactions to get test cases to pass