Region Selection 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

multiple README improvements, including a list of 3rd party repos

added support for OpenVPN

improved output and comments for better user experience

changed documentation and comments to make it easier to read through