Renamed bootloaders/isolinux to bootloaders/syslinux.
Merge branch 'make-syslinux-default-bootloader'

* make-syslinux-default-bootloader:
  Renamed bootloaders/isolinux to bootloaders/syslinux.
Added hook for copying Syslinux configuration to Isolinux configuration.

Symlinking config/bootloaders/syslinux to config/bootloaders/isolinux
breaks live-build scripts.
Configure .xsessionrc in hook instead of providing new file.
Fixed invalid lightdm-gtk-greeter variable name.