Add zfs.util.get_pool_from_fsname
Add zpool_list and get_zpool_guid

Split out the testing regexes for filesystem name components. Add a
couple of helper methods to test either a pool name or a whole dataset
name (with multiple slashes).

Add zpool_list functionality, including the ability to retrieve
information about more than one pool.

Add function to retrieve GUID of a given pool.
Fix regex bug for alphanumerics

Fix a problem where numbers weren't being tested properly. Found this
after changing test case to use a real snapshot name from an existing
zfsautosnap snapshot