Fixes Bug in FluidGridLayout when compute size

The old computeSize implementation used the parent bounds as the size
for the child. This is valid for the width but not for the height. This
commit fixes this issue by using the children sizes for computing the
height of the composite with the FluidGridLayout.

Change-Id: Icf91a6b93f83831f60906fbdbf7aa3102823fbf5
Version Bump to 1.3.1

Change-Id: I24ac40dae8c579831cc927ed04afcb9783d40f21