Simplify configuration schema

[tintoy]

Configuration is getting a little crusty and organisation is tending towards nonsensical. Rationalise it.

Old schema:

{
    "msbuildProjectTools": {
        "language": {
            "enable": true,
            "disableHover": false,
            "logLevel": "Information",
            "logFile": "",
            "trace": false,
            "seqLogging": {
                "logLevel": "Debug",
                "url": "http://localhost:5341/",
                "apiKey": "whatever"
            },
            "completionsFromProject": [
                "ItemType",
                "ItemMetadata",
                "Property"
            ],
            "experimentalFeatures": [
                "expressions"
            ]
        },
        "nuget": {
            "newestVersionsFirst": true,
            "includePreRelease": true,
            "disablePrefetch": false
        }
    }
}

New schema:

{
    "msbuildProjectTools": {
        "schemaVersion": 1,
        "logging": {
            "level": "Debug",
            "file": "Log.txt",
            "trace": true,
            "seq": {
                "level": "Debug",
                "url": "http://localhost:5341/",
                "apiKey": "whatever"
            }
        },
        "language": {
            "useClassicProvider": false,
            "disable": {
                "hover": false
            },
            "completionsFromProject": [
                "Property",
                "ItemType",
                "ItemMetadata",
                "Target",
                "Task"
            ]
        },
        "nuget": {
            "newestVersionsFirst": true,
            "includePreRelease": false,
            "disablePrefetch": true
        },
        "experimentalFeatures": [
            "expressions"
        ]
    }
}

[tintoy]

Implemented.