Add support for the sort parameter when performing a search
Merge pull request #3 from dizzyd/dss-search-sorting

Add support for the sort parameter when performing a search
Add test for sort parameter
Correct use statement in KV List section

Fixes #4
Post operation added
Alternative POST implementation

- UpsertOperationInterface to reduce duplication
- Location added to all operation getObjectFromResponse. KvPostOperation
  uses the location to get the key.
- Added test for POST and fixed other tests to support location.