syslog: fixes and updates to rsyslogd and logrotate.
Adjust lograte size to prevent a mismatch.
Change rsyslogd size to be actual size instead of a naive value.
utils/syslog: updating comments for logrotate config
Align metricsDoc.EnvUUID serialization.

Follow the multi-environment document convention of serializing EnvUUID
as "env-uuid".
Remove EnvironStorage from Environ interface

Storage is now optional; backups will fail
if the environment does not support provider
storage. None of the providers' storage
implementations has been taken away yet, so
this is not a problem in practice.
Update tests to not use Environ.Storage()
Add TODO about migrating backups
Add comment to environs.LegacyStorage
Address review comments

Reinstate some tests, fix comments, improve error message
we don't need metric.Refresh
Fix 1373611 dont fail when backup is HA
Reinstate the 1.18 compatability for AddMachines.
Merge pull request #838 from howbazaar/fix-1.18-add-machine

Reinstate the 1.18 compatibility for AddMachines.

Fixes https://bugs.launchpad.net/juju-core/+bug/1373424
Merge pull request #836 from perrito666/fix_1373611

Fix 1373611 dont fail when backup is HA

Remove a verification on restore that is outdated.
In the past it was not possible to restore to an HA environment, 
this restriction has been lifted and this error is deprecated
Merge pull request #821 from cmars/metrics-env-uuid

Align metricsDoc.EnvUUID serialization.

Follow the multi-environment document convention of serializing EnvUUID
as "env-uuid".
EnvironTag from the API connection is accessible to all facades
Merge pull request #828 from dimitern/api-environtag

EnvironTag from the API connection is accessible to all facades

Refactoring a few places to allow easier access to the current
API connection's environment tag, and a few drive-by fixes:
 - HighAvailability API's NewClient() no longer needs EnvironTag
   as a (string) argument, but discovers it via the connection.
 - MetricsManager API refactored slightly to use an AuthFunc to
   verify any given tags are valid environment tags and match
   the current environment.
 - api.Uniter() factory method changed to validate the currently
   authenticated user's tag is indeed a names.UnitTag, rather
   than possibly panicking when it's not.
 - api.Info.EnvironTag is now names.EnvironTag, rather than
   a names.Tag; tests changed accordingly.
 - Minor drive-by fixes to imports ordering and doc comments.
Better EnvironTag validation
Merge pull request #825 from axw/environs-remove-storage

Remove EnvironStorage from Environ interface

Storage is now optional; backups will fail if the environment does not
support provider storage. None of the providers' storage implementations
have been taken away yet, so this is not a problem in practice (yet).
Merge pull request #839 from dimitern/environtag-follow-up

Better EnvironTag validation

Implemented a few suggestions from http://reviews.vapour.ws/r/96/:
 - Added validation of the EnvironTag on the API connection.
 - Better checks in tests comparing EnvironTags.
add help for instance-type constraint