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

config/deb.am

@@ -47,6 +47,7 @@ deb-utils: deb-local rpm-utils
 	pkg7=$${name}-test-$${version}.$${arch}.rpm; \
 	pkg8=$${name}-dracut-$${version}.$${arch}.rpm; \
 	pkg9=$${name}-initramfs-$${version}.$${arch}.rpm; \
+	pkg10=pyzfs-$${version}.noarch.rpm; \
 ## Arguments need to be passed to dh_shlibdeps. Alien provides no mechanism
 ## to do this, so we install a shim onto the path which calls the real
 ## dh_shlibdeps with the required arguments.
@@ -62,10 +63,10 @@ deb-utils: deb-local rpm-utils
 	env PATH=$${path_prepend}:$${PATH} \
 	fakeroot $(ALIEN) --bump=0 --scripts --to-deb --target=$$debarch \
 	    $$pkg1 $$pkg2 $$pkg3 $$pkg4 $$pkg5 $$pkg6 $$pkg7 \
-	    $$pkg8 $$pkg9; \
+	    $$pkg8 $$pkg9 $$pkg10; \
 	$(RM) $${path_prepend}/dh_shlibdeps; \
 	rmdir $${path_prepend}; \
 	$(RM) $$pkg1 $$pkg2 $$pkg3 $$pkg4 $$pkg5 $$pkg6 $$pkg7 \
-	    $$pkg8 $$pkg9;
+	    $$pkg8 $$pkg9 $$pkg10;
 
 deb: deb-kmod deb-dkms deb-utils