Added entity initializers for HttpRequestSensors. Polling over a URI and retrieving a single JSON value from the response.
Add support for json-path (https://code.google.com/p/json-path) for full access to json response

Moved test to new package

Refactoring to avoid removing functionality:
now it supports both full path with JSONPath (through HttpValueFunctions.jsonContentsFromPath) and 1-level json element only.

rebased minor commits
Adds support for multiple type value on AddSensor.

Target type now needs to be specified as ConfigKey
Tests added for JsonFunctions.getPath