Add use cases for each tor-launcher option.

It's pretty common to hear things like "I don't know what any of the 'Configure' options mean." It would help users if each Tor launcher option briefly described a situation where using it would be necessary. For example:

• This computer needs to use a proxy to access the Internet. Only select if you can't use your regular browser without setting a proxy.

• This computer goes through a firewall that only allows connections to certain ports. This applies at some universities and large companies.

• My Internet Service Provider (ISP) blocks connections to the Tor network. Users in China need this option.

These are only examples of how the strings could be modified.