Integer types not being handled on the R side

In the CPLEX spec, an Integer type field is technically categorized as "General", but on the UI side we call it "Integer" so that things are clearer. However, the R code is not currently looking for anything called "Integer", and so that type is not being processed correctly.

For example, the UI provides an array of field item objects, like so:

``` JSON
[
{
"fieldName": "x1",
"type": "Continuous",
"lowerBound": 0,
"upperBound": "+inf"
}, {
"fieldName": "x2",
"type": "Integer",
"lowerBound": 0,
"upperBound": "+inf"
}, {
"fieldName": "x3",
"type": "Binary",
"lowerBound": 0,
"upperBound": 1
}
]
```

The R code, found [here](https://github.com/alteryx/AlteryxPrescriptive/blob/28f4568ad2ba7c2d3f91efc90a9ed62ae5c0b962/R/manualInputs.R#L17-L26), is attempting to match on different field types, but is not looking for "Integer", and so everything falls through to the default case and is treated as continuous.