Release 2.3.0

Quite a few things in this release:
    - Trash functionality. Configuration will now look for trash
      settings and apply them. When trash is enabled, deleting files
      will move them to trash. The Client class now also takes a
      use_trash argument. The command line client's rm command now takes
      -S or --skiptrash to skip the trash.
    - Security fix for UIDs. Snakebite would set the realUser property
      for requests to the Namenode which caused everything to be
      excecuted as the user the NN was running at, which is dangerous
      and completely circumvents security. This has been changed to use
      the effectiveUser property.
    - Config format: a new .snakebiterc format has been introduced that
      is verioned. The new format support skiptrash. Config is backwards
      compatible with both single line NN config and HA, but defaults to
      skiptrash=False for those cases.
    - ~/.snakebiterc isn't written anymore. This change is made, since
      moving cluster config was hard and users had to remove their
      .snakebiterc. It can still be used to override default settings.
    - Tests that use the java MiniCluster will not run anymore when an
      active Hadoop cluster is found (i.e. when `hadoop fs -ls /` can be
      ran from the host running the tests). This is done because in
      certain cases, the MiniCluster java class still interacts with the
      Hadoop environment (e.g. format journal nodes).

Change-Id: I50110c18cb895c5feae46c370d0184c59212054c