Add manual pages

[kfv]

We need a comprehensive list of man pages besides the help command that goes deeper into all details, lists more examples, and covers caveats, bugs, etc.

List of the required manual pages at this time:

• [x] jailer (227e225)
• [x] jailer-init (b3bbeb6)
• [x] jailer-image (1f64712)
• [x] jailer-create / jailer-destroy (6637347)
• [x] jailer-start / jailer-stop / jailer-list (16e4795)

Note: jailer-start(8) will be rewritten soon; it only warns users of the state of the interface at the moment.