Ability to format igxGrid export to excel summary values

[kcostenbader]

According to this forum post

https://www.infragistics.com/community/forums/f/ignite-ui-for-angular/126158/while-we-perform-export-to-excel-for-igx-grid-for-summary-totals-i-was-getting-colons-after-the-total-values

It is only possible to export totals from igxgrid in 'label: value' format and the colons cannot be removed.

This issue is critical for some of our customers because they cannot write formulas against the exported data.