identity: don't use getopt() in main we can't portably reset it.

identity: few fixes Correct export usage; rename variable in cmd_mappings, allow to filter by identity name.

draft of telescope-identity(1) This is intended to generate and manage certificates outside of telescope. Some operations are already available in the telescope UI, such as use and forget a certificate for a specific page, but generate and removal are hard at the moment to implement inside telescope limited UI, so provide an helper program for that.