Added type attribute on app when a column does not contain a variant.

[raffazizzi]

Hello, @ebeshero and I have been working on a collation and realized that it would be necessary for us to know whether a table object row contains normalized tokens that agree or not. So we added an attribute to <app> in the XML output that indicates whether the children <rdg>s agree. Example:

<app type="invariant">
    <rdg wit="#f1818">We were strangers to any species </rdg>
    <rdg wit="#f1823">We were strangers to any species </rdg>
    <rdg wit="#fMSc56">We were strangers &lt;lb/&gt;to any species </rdg>
</app>

In the example above the string <lb/> is set to be normalized away during the collation process; yet we need to see it in the output for project-specific reasons. This way would indicate alignment but keep the witnesses separate.

For further reference, you can find our project here: https://github.com/ebeshero/Pittsburgh_Frankenstein/tree/Text_Processing

[djbpitt]

I think this is an improvement. It doesn't seem to break anything, and since XML output is likely to be chosen in situations that will undergo subsequent processing with XSLT anyway, and that is likely to care about the presence or absence of variation, it relieves the downstream process of having to check for the presence or absence of variation within the <app>.