Add a qan perf schema worker and interval iter.  Update factories to support both types, slowlog and perfschema.
Merge branch 'release' into qan-pfs-worker
Update percona-agent/main.go with new qan factory names.
Remove qan iter running: it's vestigial, can re-implement later if needed.
Remove redundant arg from qan.MakeReport().
Test qan.ValidateConfig and require MaxWorkers >= 1.
Fix and test qan.PrepareResult().  Requires mysql-log-parser 43c98aa.
Add 'GRANT UPDATE, DELETE, DROP ON performance_schema.*' to MySQL agent user during install.
Merge branch 'release' into qan-pfs-worker

Conflicts:
	Godeps.json
Default qan.Config.CollectFrom to "slowlog" for backward-compat with existing default QAN configs. Increase log relay buffer from 10 to 50.
Merge pull request #75 from percona/qan-pfs-worker

PCT-687: Make working perf schema worker prototype