Adopt pyzfs from ClusterHQ

This commit introduces several changes:

 * Update LICENSE and project information

 * Give a good PEP8 talk to existing Python source code

 * Add RPM/DEB packaging for pyzfs

 * Fix some outstanding issues with the existing pyzfs code caused by
   changes in the ABI since the last time the code was updated

 * Integrate pyzfs Python unittest with the ZFS Test Suite

 * Add missing libzfs_core functions: lzc_change_key,
   lzc_channel_program, lzc_channel_program_nosync, lzc_load_key,
   lzc_receive_one, lzc_receive_resumable, lzc_receive_with_cmdprops,
   lzc_receive_with_header, lzc_reopen, lzc_send_resume, lzc_sync,
   lzc_unload_key, lzc_remap

Note: this commit slightly changes zfs_ioc_unload_key() ABI. This allow
to differentiate the case where we tried to unload a key on a
non-existing dataset (ENOENT) from the situation where a dataset has
no key loaded: this is consistent with the "change" case where trying
to zfs_ioc_change_key() from a dataset with no key results in EACCES.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes #7230

tests/runfiles/linux.run

@@ -646,6 +646,12 @@ tests = ['projectid_001_pos', 'projectid_002_pos', 'projectid_003_pos',
     'projecttree_001_pos', 'projecttree_002_pos', 'projecttree_003_neg' ]
 tags = ['functional', 'projectquota']
 
+[tests/functional/pyzfs]
+tests = ['pyzfs_unittest']
+pre =
+post =
+tags = ['functional', 'pyzfs']
+
 [tests/functional/quota]
 tests = ['quota_001_pos', 'quota_002_pos', 'quota_003_pos',
          'quota_004_pos', 'quota_005_pos', 'quota_006_neg']