[TASK] Adjust icons in EXT:belog

* Warnings are displayed by FontAwesome now
* Errors are now represented as a circled exclamation mark

Resolves: #65080
Releases: master
Change-Id: I424cf4bbfe93dd8a4f48e4904050f4be87bc282e
Reviewed-on: http://review.typo3.org/38636


Reviewed-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Tested-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Reviewed-by: Xavier Perseguers <xavier@typo3.org>
Tested-by: Xavier Perseguers <xavier@typo3.org>