Implemented converter into human readable format.

Main changes:
- Created new binary, called `uncork-flaschenpost`
- Defined a (rather pointless) default for `module` to prevent errors on reading incomplete (or wrong) log data.
  Nice side-effect: You can call `flschanpost.use('module', ...)` after `flaschenpost.getLogger()`
- For the same reason, defined `info` as log level if it's missing in the source data.
- Introduced new function `paragraph` that converts a given `blueprint` into a pragraph object. It can be used to re-read logs since a paragraph can serve as a blueprint again. Used by `letter/index.js`, too.