Add functionality for PUT requests

[Suocesky]

Add functions to accept and handle PUT requests in addition to POST requests so that values can be edited from the web app.

[jgfoster]

The goal of this task is to support editing selected fields from the current information table (see EthernetServer_TC.cpp:132). The general format will be similar to a POST but is a PUT with a key from the list in JSONBuilder.cpp:37-49 and a new value for that field. On success the server should return a status code of 200 and the body content from the current() function (above).

[jgfoster]

The steps we will do for this include the following:

• Fork to your personal GitHub account
• Clone to a local environment or to Code.CS in a Ruby workspace (our application is in C++ but the testing framework is Ruby)
• Confirm that the tests pass with ./extras/scripts/testAndBuild.sh
• Copy the tests for POST but make it for PUT, confirm that they fail, then add/edit code to them pass
• Change the tests to support different keys, confirm that they fail, then make them pass
• Change the tests to support different return values (current() instead of display()), confirm that they fail, then make them pass

[jgfoster]

Fixed by #389.