SPHERE-197 Add CustomObjectService
SPHERE-197 Add method to retrieve custom object
SPHERE-197 Add method to set custom object
Add interface method
Implement DELETE requests and use them for custom objects
Add test implementation
Add spec for custom object deletion
Strip whitespace
Move types into correct packages~
Add necessary adapters for DELETE requests to SDK
Use imports instead of long type names
Add custom objects to Sphere
Add toString
Improve Javadoc
Add marker interface
Merge pull request #2 from commercetools/SPHERE-197-key-value-store

Add custom object storage