Switch to Jackson for JSON parsing for OTP Server responses, instead of Simple XML and XML

[barbeau]

This will allow us to use JSON instead of XML on Android, and will hopefully make future updates to new OTP server REST API versions easier since with Jackson few class annotations are required. Using Simple XML, we'd had to strip out the server-side annotations, then re-annotate with Simple XML annotations. Jackson has only required a few annotations so far.

See this page for details:
https://github.com/CUTR-at-USF/OTP-Java-Client/wiki/HOWTO-modify-code-to-reflect-changes-from-main-OTP

[barbeau]

Original testing for this only included a URL for walk-only trips. Upon testing with transit trips that include additional elements in the JSON response, we still have to resolve a few errors with these objects.

[barbeau]

Fixed in a series of commits, ending with 2b8fd68.