Correct typos.
Implement separated portstree feature.

   * We do not want to pollute our basesystem or our own portstree with
     poudriere's portstree: install it into /usr/local/poudriere.
Check if PORTSDIR is defined before launching portsnap.
Make portsnap less verbose.
Hardcode everything is a bad habit.

  * Replace /usr/ports by ${PORTSDIR}

  * While here, correct a typo
Do not rebuild already existing packages

In bulk we now make sure that everything is clean before using it.
also skip build things that already exists
restart from a fresh jail (no packages) between two builds in bulk
Better error handling, if something goes wrong now poudriere always return != 0
Allow plural for "poudriere lsjail" command.
new subcommand ports

ports -c -p <name> create a portstree named "name"
ports -d -p <name> delete a portstree named "name"
ports -d -p <name> update a portstree named "name"
ports -l lists all available portstree

All the other commands have been update to have a new argument -p
<portstreename> defaulting to "default"

So if you create a ports tree named "default" nothing will change for you

ports only uses portsnap however you can create custom portstree by hand, just
create a jail ${ZPOOL}/poudriere/ports-<name> mounted where you wanted it to be
mounted
then create a ports/ directoty in that mointpoint
populate this ports directory with csup for example
Merge branch 'master' of etoilebsd.net:poudriere
Update doc and add a default behaviour.
Update doc.
Consistency and readability.
Remove trailing whitespace.
More doc, typo fixes, etc.
Remove action unicity on a given portstree.
Remove a useless clean
Fix typo in test_ports.sh
Get rid of the ld.so.hints warning (only work in new jails)
Remove annoying debug message.