Added --env option to specify an -env paramter to pass to OpenOffice/LibreOffice.

The OpenOffice/LibreOffice (OO/LO) -env option allows us to set the OO/LO home directory and thus allows us to run several listener instances simultaneously to do parallel conversions.

Here is an example of starting two listeners and then converting two files in parallel.

/tmp/aoo/openoffice.org3/program/python /tmp/aoo/unoconv-master/unoconv '--port=8101' '--env=UserInstallation=file:///tmp/.oo1' '-l' &
/tmp/aoo/openoffice.org3/program/python /tmp/aoo/unoconv-master/unoconv '--port=8102' '--env=UserInstallation=file:///tmp/.oo1' '-l' &

# Let the listeners start
sleep 5

/tmp/aoo/openoffice.org3/program/python /tmp/aoo/unoconv-master/unoconv '--port=8101' '--env=UserInstallation=file:///tmp/.oo1' '--timeout=10' '--no-launch' '-o' '/tmp/convert_1/warmup' '-e' 'Watermark="WARM UP!"' '-f' 'pdf' '/tmp/test.docx' &

/tmp/aoo/openoffice.org3/program/python /tmp/aoo/unoconv-master/unoconv '--port=8102' '--env=UserInstallation=file:///tmp/.oo2' '--timeout=10' '--no-launch' '-o' '/tmp/convert_2/warmup' '-e' 'Watermark="WARM UP!"' '-f' 'pdf' '/tmp/test.docx' &