Jd class

The first part of a C++ class to get / upload from isense.
Currently only pulls fields and posts using contributor keys.
In the future I'll add email / password support, as well as a few other API functions.
Requires picojson to make. Also, 'value' and 'object' are picojson objects.
@stowellm @bdonald25
Perhaps a more suitable comment
```
// Let's add a timestamp using the provided generate_timestamp() method by the iSENSE class
```