Accept full config in testing tab

[dugite-code]

The testing tab should be smart enough to be able to accept a full config like:

{
"xkcd.com":{
    "type": "xpath",
    "xpath": [
        "div[contains(@id,'comic')]",
        "div[contains(@id,'comic')]\/img\/@title"
    ],
    "join_element": "<p \/>"
}
}

as well as the limited config

{
    "type": "xpath",
    "xpath": [
        "div[contains(@id,'comic')]",
        "div[contains(@id,'comic')]\/img\/@title"
    ],
    "join_element": "<p \/>"
}