remove -v from gg undocumented flag to dump to stdout the request before doing it. Not useful, it's debugging leftover.

fix gg -P flag description: the `:' is in the optional part


fix and sync gg usage

reimplement gg This is a better version of gg. Initially it grew with flags directly needed to the specific test cases I wanted to write, so it's ugly to use but handy for tests. This is a new and re-thought implementation that it is (hopefully) easier to use both and "curl-like for gemini" but also for scripts and tests cases. One completely new feature is the proxying support with -P to send the request to the given host.