Replace Jackson parser with a JSONObject

[rotemmiz]

Our invocation protocol uses JSON to pass instructions from the node process (tester) to the device (testee).
The Android implementation of the invocation mechanism uses Jackson ObjectMapper to parse the JSON input automatically by mapping the JSON string into a POJO (meaning there’s no need to write custom JSON parsers). This was a very fast and easy implementation but using Jackson in a library project was a mistake, as mentioned in #334 , it may easily cause collisions with the users applications if they use Jackson in their projects (it's a pretty popular library).

We need to replace Jackson's parser, instead we can use the built in org.json.JSONObject and create manual parsers to parse the following objects.

Parsing the invocation objects is fully tested and should be pretty easy to and safe to replace.
The main part of the implementation is in JsonParser.

[DanielMSchmidt]

@rotemmiz I tried to solve this issue, and I think I was on a good track, and "finished" a part of the integration. When I wanted to try it out I got a strange result, JSONObject seems to always return null. I could reproduce is in two tests in a nice and small diff: 88f884d

I think I am missing a small point, but I can't find it 😭 Could anyone lend me an eye on this?