[TASK] Base FlashMessage CSS on Bootstrap

Use Bootstrap CSS for FlashMessages.
Also use TYPO3 standard status colors in Bootstrap.

Resolves: #61586
Releases: master
Change-Id: I8d5b98f71d83db3371c59838aefc031b12dbd278
Reviewed-on: http://review.typo3.org/32771
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Frank Nägler <typo3@naegler.net>
Tested-by: Frank Nägler <typo3@naegler.net>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>