Imported initial version

Signed-off-by: Markus Frosch <markus@lazyfrosch.de>
Disabled unused icinga_sla_periods
Fixed problems with series calculation

* start / end of sla was labeled wrong
* no overlapping between day periods
  (dt and sla of last day in current day)
* ordering of sla start / end
* Added duration
Added debug_sladetail procedure for verbose output

Can also be used to list event details in SLA periods.
Added update_holiday procedure to set certain days as holiday

Has to be run for every day that is a holiday, after the
data refresh.
Added COPYING and LICENSE information
Added example report to list SLA performance of a hostgroup

For its hosts and services.
Renamed filenames to match database names
Move away old procedures
Add new cache procedure and availability function
Cleanup old stuff
Move SQL files in subdir
Renamed functions for a proper namespace
Fix double bracket
Always use MEMORY for eventcache
Add cleanup SQL for older SLA function sets
Use Icinga Team in copyright
Move README to docs
Update SLA docs
Fix cached event data query