[BUGFIX] Backend Layout Grid Wizard not fully visible in Mac Firefox 22

Under Firefox the outer table's height and width of the backend layout
wizard is set to 100%. Since there is content before the table, this
leads to the table being cut of, as there are no scrollbars. According
to the suggestion of Philipp Gampe the table's height and width are
changed to 90%.

Resolves: #50424
Releases: 6.2, 6.1, 6.0, 4.7, 4.5
Change-Id: I589fdfd8de0a8d6ebb4b3ee4fd2a173341116016
Reviewed-on: https://review.typo3.org/23513
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe