Add share/ltsp/plugins/ltsp-build-client/Debian-custom/095-squashfs-image
to enable setting it; see #904427 (LTSP) why this is needed.

Add etc/ltsp/ltsp-build-client.conf with settings for NFS.

Adjust sbin/debian-edu-pxeinstall and accordingly to be able to use NFS on
the main network as well.

Rework cf3/cf.homes:
 Write /etc/export file with profile and architecture dependent values.
 Drop no longer needed nfs-{common,kernel-server} configuration edits.