Add ManagedResource. Update FileHandler, tests

* FileHandler: changed return type of getCsvContent. Either not needed since no validation, Option better than returning empty Map.
* FileHandlerSpec: implemented tests for getCsvContent.
* ManagedResource: new object for handling files mainly.
* Added some more test-data.
Merge branch 'master' of https://github.com/ssfc/test_step

* README.md changed in github web GUI.