-- Introduce proper space calculation by each boot environment in *beadm list*
-- Rework the *beadm destroy* command so no orphans are left after destroying boot environment.
-- Fix the *beadm mount* and *beadm umount* commands error handling.
-- Rework consistency of all error and informational messages.
-- Simplify and cleanup code where possible.
-- Fix *beadm destroy* for 'static' (not cloned) boot environments received by *zfs receive* command.
-- Use mktemp(1) where possible.
-- Implement *beadm list -a* option to list all datasets and snapshots of boot environments.
-- Add proper mountpoint listing to the *beadm list* command.
   % beadm list
   BE      Active Mountpoint       Space Created
   default NR     /                11.0G 2012-07-28 00:01
   test1   -      /tmp/tmp.IUQuFO  41.2M 2012-08-27 21:20
   test2   -      -                56.6M 2012-08-27 21:20

-- Change snapshot format to the one used by original *beadm* command
(%Y-%m-%d-%H:%M:%S).
   % zfs list -t snapshot -o name -r sys/ROOT/default
   NAME
   sys/ROOT/default@2012-08-27-21:20:00
   sys/ROOT/default@2012-08-27-21:20:18

-- Implement *beadm list -D* option to display space that would be consumed by single boot environment if all other boot environments will be destroyed.
   % beadm list -D
   BE      Active Mountpoint       Space Created
   default NR     /                 9.4G 2012-07-28 00:01
   test1   -      /tmp/tmp.IUQuFO   8.7G 2012-08-27 21:20
   test2   -                        8.7G 2012-08-27 21:20

-- Add an option to BEADM DESTROY command to not destroy manually created snapshots used for boot environment.

   # beadm destroy test1
   Are you sure you want to destroy 'test1'?
   This action cannot be undone (y/[n]): y
   Boot environment 'test1' was created from existing snapshot
   Destroy 'default@test1' snapshot? (y/[n]): y
   Destroyed successfully

   # beadm destroy test1
   Are you sure you want to destroy 'test1'?
   This action cannot be undone (y/[n]): y
   Boot environment 'test1' was created from existing snapshot
   Destroy 'default@test1' snapshot? (y/[n]): n
   Origin snapshot 'default@test1' will be preserved
   Destroyed successfully