client: use pam_exec at auth to create session cache dirs

This allows us to centralize mkdiring
client: quote shell string variable to avoid nasty whitespace bugs
client: strip puavo-pam- prefixes from library scripts
client: chown works only in PAM session phase
client: make pam scripts fail early
client: rename printer setup xsession script
client: fix typo
client: fallback to fi in locale/language setup