Add misc/write_PWD_from_env_vars.sh - writes a PWD file using
environment variables:

    UID=${TDSPWDUID}
    PWD=${TDSPWDPWD}
    SRV=${TDSPWDSRV}
    DB=${TDSPWDDB}
Merge branch 'write_PWD_from_env_vars' into travis3
.travis.yml: Add call to misc/write_PWD_from_env_vars.sh to write PWD
file