Turn getSnapshots*() into forEach*(), move snapshot query implementations into Entity, fix deprecation warnings

added JSON conversion to Aron code generation, first working version of motion memory, added a addInstance method to Snapshot

Make mongocxx install script more user friendly. Add a clear warning with what to do if mongocxx is missing.

new lib armem_robot and armem_robot_state => armem_robot is base for armem_robot_state and armem_objects

Revise armem core; remove virtual inheritance. Move constructors to base classes. Remove copy ctors and operators

renamed stuff, added namespaces to base classes, shortened namespaces of memories, fixed robotsensormemory memory name