Use BS Alerts instead of gritter (#4812)

Use BS Alerts instead of gritter (#4812)

* Use BS Alerts instead of gritter

Replacing package used to display messages by Bootstrap's alerts.

* Modify previous commit

Add hidden alert tag html.

* Standard javascript version

Replaced use of jQuery

* Update prior commit

Easier to remove - effectively alert('dispose') instead of alert('close').
If needed, bsAlert should be called again rather than manipulating hidden alert element.