region selection, colors and other improvements

• separated get_region and get_token into two separate scripts, allowing for independent calls to each if desired; this also allows the implementation of other features mentioned below
• implemented use of new centralized authentication server for easier automation; the new API is located at https://privateinternetaccess.com/gtoken/generateToken
• added server selection capabilities to run_setup.sh, as requested by multiple users
• added one-line call capabilities to run_setup.sh to allow easy automation
• changed PIA_AUTOCONNECT to VPN_PROTOCOL for clarity
• added AUTOCONNECT for one-line calls
• added PREFERRED_REGION for one-line calls
• added colored output to highlight important details
• added input validation for prompts in run_setup.sh