Fix comment about the default DiskStartSector size
Pass along the DataAlignment to LVM and LUKS
Use value of provided DiskAlignment for DiskStartSector

If a value for DiskAlignment is provided by the user it is also used as
base for DiskStartSector.
If DiskStartSector is specified by the user it doesn't get overriden.
Adapt getSector to consider DiskAlignment values in KB
Show information about disk alignment during build
Added unit information to default values in KIWIGlobals
Also set default disk alignment to 4 KB
Set disk alignment default value to 1 MB

A value of 1 MB should be fine for most SSDs and doesn't have any impact
on regular hard disks.
It can be changed with the parameter --disk-alignment.
Merge pull request #380 from openSUSE/handover_alignment_parameters

Pass along DiskAlignment to LVM and LUKS