Updated docs: use .wid instead of .conf
 - some test improvements
 - re-adding wrongly removed code
 - fixing some failing bpmn2 persistence tests
fixed tests that failed with enabled persistence
JBPM-3832 - Provide API method to delete session from db
Fixing scope to entity managers of Execution Service
 - updating out-of-date test
 - adding a few more utility methods to trigger nodes
Minor fixes to the documentation
JBPM-3913: Handle all exceptions in process instances with ExceptionScopeInstances if appropriate
JBPM-3913: Modified and added new WorkItemHandlers for exception handling

- also cleaned up invalid and unused code in jbpm-workitems
JBPM-3913: Extended support for event handling in event subprocesses

- event contents are now passed to the event sub-processes
- extended support for <error> and <signal> (and associated (error|signal)EventDefinition elements)
JBPM-3913: Exception handling tests (and clean up of other bpmn2 tests)

 - Tests for the SignallingTaskHandlerWrapper + Event Subprocess improvements
   - Tests for passing event contents to event subprocesses
 - Added the ExceptionService class that's used in the BPMN2-ExceptionServiceProcess* files
 - Moved some tests from JUnit 3 to 4 (@Test instead of "extends TestCase")
 - Remove duplicate TestWorkItemHandler implementations and refactored it to it's own class
 - updating out-of-date test
Merge pull request #127 from psiroky/docs-wid-ext

Updated docs: use .wid instead of .conf
 - fixing out-of-date test
Correction to executor retries, allows all types of raw data for retries context parameter
Exposing executor service status from the entry point
Added query method with status parameters