Put in a switch to detect and use Orbot if present

[yaronyg]

We want to use this library so that people don't have to do things like install Orbot. But the library has a toll if the user is using multiple Tor apps. It will take more memory, more bandwidth, etc. So ideally what we should do is detect if Orbot is installed and then turn off our own TOR functionality in favor of Orbot's. There is a nice NetCipher library for working with Orbot, see here.