New backend, minor bugfixes and new features

• add a new, faster backend as an alternative to fanotify: a custom kernel-module
  based on the kernel-internal tracepoints and the ftrace-framework
• fix a bug where certain file events were not registered from within the (fanotify-based) shell integration
• deduplicate file-event-paths in the database to save disk space
• add limits for max. count of read/write-events per command
• limit database write-speed in order to be nice to other processes
• Provide a shournal-edition for Docker (and other container-platforms) and
  document how to use it
• shournal-run now allows for a user-provided $TMPDIR (applies automatically if used
  from the shell-integration or the wrapper-binary shournal)