Dict dictionary protocol backend

* Implements a dict protocol client and a dictionary registry
* Exposes a REST api dictionary/:word/:from/:to

Example: http://localhost:8000/dictionary/pen/en/de
Result:
{
  "definitions": [
    {
      "def": "pen /pen/\r\n (Schreib-) Feder; Füller; Griffel <m>; Stift <m>",
      "db": {
        "name": "fd",
        "desc": "English-German FreeDict Dictionary ver. 0.3.5"
      }
    }
  ],
  "suggestions": []
}

Change-Id: I138b5d457ce46c5bfe4e760d95f29c3adf25abfd
Dictionary: Json file dictionary backend

* Reads dictionaries from json files
* Introduce toolset registry to pick suitable dictionary providers
* Use a consistent return format:
{
	"source": "manzana",
	"translations": [
		{
			"phrase": "apple",
			"info": "(noun)",
			"sources": ["fd-spa-eng"]
		},
		...
	]
}

Change-Id: Ifddfd359ebdbfbfdc1b26a70cdd29949ee230f40
Merge changes Ifddfd359,I138b5d45

* changes:
  Dictionary: Json file dictionary backend
  Dict dictionary protocol backend