Refactor flag parsing and logging

[afritzler]

Proposed Changes

Use idiomatic golang flag parsing. Use propper logging setup instead of custom logger with custom flags.

Usage of ./bin/fedhcp:
  -config string
        config file
  -kubeconfig string
        Paths to a kubeconfig. Only required if out-of-cluster.
  -list-plugins
        list plugins

This is a breaking change as the flag names have changed.