Avoids collisions of Downtime.id between schedulers

Each scheduler starts Downtime.id from 1 and increments it by 1 at each
downtime creation. So, when running multiple schedulers, multiple
downtimes will have the same ID. Commands like DEL_SVC_DOWNTIME are
broadcasted to all schedulers for execution. When deleting a downtime,
if the ID is not unique, all the downtimes that have the same ID will be
deleted. By using microseconds since 1970-01-01 as an ID, the probability
of collision is reduced.
Fix copy pasted doc?
Merge pull request #1189 from ppepos/patch-1

Fix copy pasted doc?
Merge pull request #1188 from rledisez/master

Avoids collisions of Downtime.id between schedulers
Enh : Test - Begin hand made merge of #608
Update doc-string.
Enh : Test - Add Docstring
Enh : Test - Keep on merging
Enh : Test - Keep on merging
Enh : Test - End merge, close #608
fix comment
Enh : Doc - Begin to add simple diagram class
Enh : Doc -Add simple diagram class for Clients package
Enh : Doc - Add simple diagram class for Daemons package
Enh : Doc - Add simple diagram class for Objects package
Enh : Doc - Add simple diagram class for Shinken package
Enh : Doc - Add simple diagram class for Exceptions
Enh : Doc - Add simple diagram class for Webui package
Enh : Doc - Add simple diagram class for Misc package
Enh : Doc - Add monitoring-plugins as conditional requirement