Cleanup async specs
Embed jsonlib in RestHelpers

- Make json methods Private
- Prefix with json_
- Rename `FilterModel` to `FilterObject`
Add helpers and cleanup

- RunCallback
- CreateResponse and CreateResponseFromHttp
Update specs and add export specs script

- Add RestHelpers specs
- Add header to specs
- Add export-specs build script
Fixes for RestHelpers
Add RestClientBase and specs
Cleanup
Add updates to library workbooks
Merge pull request #8 from timhall/refactor

Refactor