expose 'interpreted' rawValue for numbers

[McFoggy]

as exposed in #636 sometime if you want to print back recognized values you need to have a raw representation of the float value in a slot.

When the input contains already a "string number" representation of the value like below with "rawValue": "12.7" it is possible to round the numerical value at the same number of expected decimals than the ones provided inside the input:

{
    "range": {
        "start": 16,
        "end": 20
    },
    "rawValue": "12.7",
    "value": {
        "kind": "Number",
        "value": 12.699999809265137
    },
    "entity": "snips/number",
    "slotName": "data"
}

But when the input is in the form "rawValue": "twelve dot seven", it becomes difficult to do the rounding correctly

{
    "range": {
        "start": 16,
        "end": 32
    },
    "rawValue": "twelve dot seven",
    "value": {
        "kind": "Number",
        "value": 12.699999809265137
    },
    "entity": "snips/number",
    "slotName": "data"
}

Would it be possible to extend the data model to introduce some kind of rawNumberValue or rawInterpretedValue either at the slot level or at the slot.value level like in the following example:

{
    "range": {
        "start": 16,
        "end": 32
    },
    "rawValue": "twelve dot seven",
    "value": {
        "kind": "Number",
        "rawNumberValue": "12.7",
        "value": 12.699999809265137
    },
    "entity": "snips/number",
    "slotName": "data"
}

[adrienball]

Interesting indeed. In parallel, another idea would be to enrich the snips/number builtin entity by adding a precision attribute, so that you have something like:

{
    "range": {
        "start": 16,
        "end": 32
    },
    "rawValue": "twelve dot seven",
    "value": {
        "kind": "Number",
        "precision": 1,
        "value": 12.699999809265137
    },
    "entity": "snips/number",
    "slotName": "data"
}

[McFoggy]

@adrienball yes a precision field is also a perfect valid answer to the need