Add non-interactive batch mode option for install.sh

We are trying to write an ansible playbook to automate new Sametime installations, but the current install script only takes inputs interactively. The option to pass inputs programmatically instead of through a user at a keyboard would be very helpful.

One workaround we considered was to simply remove every 'read' line from the install script and set the environment variables ourselves before running it, but even that won't work since you reuse the CHOICE variable throughout the installation process.

A simple solution for this would be to document the input variable names, give each CHOICE a unique name, and disable the reads based on an input flag. You could go further and accept each input as an argument to the script. Either way works for us.