[TASK] Installtool: display maximum allowed file size for uploads

Since the maximum file size for uploaded files is only limited by
PHP, we could add information about the actually allowed file
size for uploads.

Releases: master
Resolves: #71663
Change-Id: I61ee372c803394a28071ed8d752b28602ef55232
Reviewed-on: https://review.typo3.org/44775


Reviewed-by: Frank Nägler <frank.naegler@typo3.org>
Tested-by: Frank Nägler <frank.naegler@typo3.org>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>