v0.6.0: Alpha release

This release adds a number of minor features:

• Better behaviour when boot fails. User can choose an action from reboot, resume boot process,
  start the "recovery" service, or power-off.
• New service settings for limiting resources at the process level: "rlimit-nofile",
  "rlimit-core", "rlimit-data", "rlimit-addrspace". Both hard and soft limits can be set.
  See dinit-service(5) for details.
• New "env-file" setting allows per-setting environment to be specified via a file. The file
  is re-read each time the service process is started.
• Added a "--quiet" option to suppress console output from Dinit.
• Dinit when run as a user daemon no longer logs via syslog. Logging to file can still be
  enabled via the "-l"/"--log-file" option.
• Added a "--socket-path"/"-p" option to dinitctl, to specify the socket path for communication
  with the dinit daemon.

A number of minor bugfixes and other improvements are also implemented. An integration test
framework has been added with a small number of tests, to complement the existing unit tests.