event stream from watcher should have logical ordering.

ie. you shouldn't publish a relation in the event stream, before the services in the relation. clients should be able to assume the output is coming, rather than rebuffering and doing ordering themselves.

Proper order is removes before adds, and then changes. Each of those sections has ordering by type, so i see machine added, service added, and then unit added.

here's an example of the issue, empty env, then deploy mysql

[u'relation', u'change', {u'Endpoints': [{u'ServiceName': u'mysql', u'Relation': {u'Name': u'cluster', u'Limit': 1, u'Scope': u'global', u'Interface':\
 u'mysql-ha', u'Role': u'peer', u'Optional': False}}], u'Key': u'mysql:cluster'}]
[u'service', u'change', {u'Life': u'alive', u'CharmURL': u'cs:precise/mysql-26', u'Name': u'mysql', u'Exposed': False, u'Config': {}, u'Constraints': \
{}}]
[u'unit', u'change', {u'Status': u'pending', u'CharmURL': u'', u'Name': u'mysql/0', u'Service': u'mysql', u'PublicAddress': u'', u'Series': u'precise'\
, u'Ports': [], u'StatusInfo': u'', u'MachineId': u'1', u'PrivateAddress': u''}]
[u'machine', u'change', {u'InstanceId': u'', u'Status': u'pending', u'StatusInfo': u'', u'Id': u'1'}]