TYPO3 Core

The error screens like "The current username, password or host was not accepted when the connection to the database was attempted to be established!" are not customizable. The image shown could be set in $TBE_STYLES in PHP, but is not changeable in the install tool

This patch moves the HTML code into a template file, makes template file and the displayed image configurable in the install tool.
Furthermore the patch does some code cleanup, because the code for the error templates existed twice - once for FE and once for BE.

In order to get such an error screen, I removed $typo_db_password from localconf.php.

(issue imported from #M15576)