refined init_model: allow change of buffer name as caused by "Save as", for example;
avoid init_model while buffer.isLoading -- potentially prevent NPE of getText;
avoid emitting nested buffer.propertiesChanged events;
#!/usr/bin/env bash
#
# psbooklet - rearrange pages of ps file to be printed as booklet (duplex)
psbook "$@" | \
pstops '4:0L@.7(21cm,0cm)+1L@.7(21cm,14.85cm),3R@.7(0cm,14.85cm)+2R@.7(0cm,29.7cm)'