TYPO3 Core

In an attempt to bring self-monitoring to TYPO3 this is the first step to achive this.
When opening the status report the highest severity of all status checks is determined and stored in TYPO3's registry.

When an admin logs in the registry is checked and if a severity higher than OK is found the warning box is enabled reporting that issues have been found, linking to the status report for more details.

By clicking the link the report is shown and the highest severity is recorded again. Now the user has seen what issues have been found and will go to fix them. Once fixed, he comes back to confirm the fix with the status report, again recording the highest severity.

Once all issues are fixed the recorded highest severity is equal or below the threshold triggering the warning box, making it disappear.

(issue imported from #M16337)