SingleQuery + Tree: Added rows under expanded parents do not render with the correct indentation

[kfranqueiro]

Steps to reproduce with code below:

1. Expand item 1 (which will also select it since you clicked it)
2. Click Add button
3. Notice that child ends up rendered with no indentation (level 0)

This happens regardless of how many children you add. If you select 1, don't expand, and add a child, when you expand the child will be rendered at the correct indentation, but any subsequent items added under item 1 after it's expanded will have the same problem.

<button id="add" type="button">Add child to selected item</button>
<div id="grid"></div>

require([
    'dojo/_base/declare',
    'dgrid/Grid',
    'dgrid/demos/laboratory/grid/SingleQuery',
    'dgrid/Selection',
    'dgrid/Tree',
    'dgrid/test/data/createHierarchicalStore'
], function (declare, Grid, SingleQuery, Selection, Tree, createStore) {
    var store = createStore({ data: [] });
    var grid = new (declare([ Grid, SingleQuery, Selection, Tree ]))({
        columns: {
            id: {
                renderExpando: true,
                label: 'ID'
            }
        },
        collection: store.getRootCollection(),
        selectionMode: 'single'
    }, 'grid');

    var nextId = 0;
    store.addSync({
        id: ++nextId,
        hasChildren: true
    });

    document.getElementById('add').onclick = function () {
        var selected = +Object.keys(grid.selection)[0];
        if (!selected) {
            return;
        }

        store.addSync({
            id: ++nextId,
            hasChildren: true,
            parent: selected
        });
    };
});

[kfranqueiro]

I have a fix for this, and I verified that I can cleanly rebase the branch for #1260 on it and it still works. Probably going to go ahead and work on bringing in SingleQuery and adding a few tests pursuant to #1271 then merge this with that.

[kfranqueiro]

I need to re-approach this fix. My original attempt moves all computation of indentation level to insertRow, which is problematic for subsequent refreshCell calls.

[kfranqueiro]

I've fixed the fix (yo dawg) and added another test for the second issue. I've also confirmed that my branch now resolves the issue as I originally discovered it in my application.

I'm going to look at #1277, then probably merge both at the same time.