SMAPI health

[Bischoff]

This PR adds the missing fields to the output of "Report health of SMAPI" (see issue #774).

It preserves ascending compatibility by introducing a new API call with a slightly different URL: GET /smapi_health instead of GET /smapi-healthy. The old call still exists with the old behaviour, but is documented as "deprecated".

• [x] new call
• [x] documentation
• [x] python client library
• [ ] unit test ?? did not find where to put one

Before

{
    "SMAPI": {
        "totalSuccess": 0,
        "totalFail": 0,
        "lastSuccess": "",
        "lastFail": "",
        "continuousFail": 0,
        "healthy": True
    }
}

After

{
    "rs": 0,
    "overallRC": 0,
    "modID": null,
    "rc": 0,
    "errmsg": "",
    "output": {
        "totalSuccess": 0,
        "totalFail": 0,
        "lastSuccess": "",
        "lastFail": "",
        "continuousFail": 0,
        "healthy": True
    }
}