[BUGFIX][!!!] Problems with new Card Layout in backend modules

There are warnings with backend modules concerning the new _JSINIT array.
To avoid these problems, this patch improves the way the module array is handled.

Module names starting with an underscore character "_" are not considered anymore.

Change-Id: Id749538dd8ee570581cb49df172800ec76242041
Releases: 4.6, 4.5
Resolves: #28523
Reviewed-on: http://review.typo3.org/3820
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader
Reviewed-by: Susanne Moog
Tested-by: Susanne Moog