(#4270) Improvements for ClassAdLogPlugins.  Allow schedd plugins by default.  Don't crash if GetJobAd() is called before the job queue is initialized.  Add BeginTransaction() and EndTransaction().  Export ScheddGetJobAd() (avoid name collision with client API).  Move BinaryLookup() to make it available outside the param table.
Merge remote-tracking branch 'origin/V8_1_5-branch'