[API] add nested request support through fields array notation

- Add ajax simple call (instead of multicall with one call) suport when bypassing multicall
- Invert multicall bypass parameter (DM.api(..., false) become (DM.api(..., true))
- Add few API tests to ensure support for nested request and fields syntax
Merge pull request #13 from happypoulp/api

Add nested request support through fields array notation (support through fields string notation already exists).