Feature: Improve usability

This includes a few usability improvements.

- Addresses problems like (https://github.com/terlar/fry/issues/2). First of by removing error output on certain invalid arguments, and secondly by having more helpful output to the commands that state the usage.
- Streamline help output.
- Add `help`, `-h`, `--help` options where it makes sense.
- Add possibility to configure through `fry config` to make options more discover-able.