fix(Tree View) Row expansion when Tree View and Select both enabled

[benjamin-wilson]

#4607
When Tree View and Select are both enabled, the Tree View expand button
did not work. The Tree View expand button was in a cell header class
who's click events are disabled. Enabling the pointer events on the
tree-header-row class resolves the issue.

[dlgski]

I found this fix was done in the wrong order. I found with:

 enableRowSelection: true, enableFullRowSelection: true, enableRowHeaderSelection: false, 

my cell is rendered with the following div:

<div ng-repeat="(colRenderIndex, col) in colContainer.renderedColumns track by col.uid" ui-grid-one-bind-id-grid="rowRenderIndex + '-' + col.uid + '-cell'" class="ui-grid-cell ng-scope ui-grid-disable-selection ui-grid-coluiGrid-0007 ui-grid-row-header-cell" ng-class="{ 'ui-grid-row-header-cell': col.isRowHeader }" role="rowheader" ui-grid-cell="" tabindex="-1" id="1450099884304-0-uiGrid-0007-cell"> 

note, in CSS the order of the classes is important so the fix here did not match. You need to re-order the classes like so:

.ui-grid-tree-header-row .ui-grid-cell.ui-grid-disable-selection.ui-grid-row-header-cell { pointer-events: all; } 

to catch this fix

[dlgski]

also note, this fix is to override: (in expandable.less)

 .ui-grid-cell.ui-grid-disable-selection.ui-grid-row-header-cell{ pointer-events: none; } 

so it makes sense to keep the order of the classes the same