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

scripts/Makefile.am

@@ -31,11 +31,14 @@ export ZEDLET_ETC_DIR=$$CMD_DIR/zed/zed.d
 export ZEDLET_LIBEXEC_DIR=$$CMD_DIR/zed/zed.d
 export ZPOOL_SCRIPT_DIR=$$CMD_DIR/zpool/zpool.d
 export ZPOOL_SCRIPTS_PATH=$$CMD_DIR/zpool/zpool.d
+export CONTRIB_DIR=@abs_top_builddir@/contrib
+export LIB_DIR=@abs_top_builddir@/lib
 
 export INSTALL_UDEV_DIR=@udevdir@
 export INSTALL_UDEV_RULE_DIR=@udevruledir@
 export INSTALL_MOUNT_HELPER_DIR=@mounthelperdir@
 export INSTALL_SYSCONF_DIR=@sysconfdir@
+export INSTALL_PYTHON_DIR=@pythonsitedir@
 
 export KMOD_SPL=@SPL_OBJ@/module/spl/spl.ko
 export KMOD_SPLAT=@SPL_OBJ@/module/splat/splat.ko