ACT-1963 Data Object support for Activiti Modeler

Removed the joda dependency for XML and JSON conversion and used default
SimpleDateFormat similar to the runtime due date values.

Updated the xml conversion code and tests to use the same formats
simplified the test comparison (got rid of Calendar code).

Fixed NPE when data objects have no value - similar issue to ACT-2005
for Designer code.

Change Id: 6b6768fea020d4bf6907866652f4262f8bb0fee1
Added feature that allows a Camel header to be used for setting the
Initiator on the workflow instance.
Added a section to User Guide on how to override SessionFactory and
plugin new classes for custom identity management solution.
ACT-2083

Autolayout fails with subprocess data objects

Added dependency on converter code so I could add a conversion unit test
that adds BPMNDI values to a template with only the BPMN model
information.
fix ACT-2093 use x to replace y
previous commit forget the center condition
Dataobjects fix for autolayout
Merge branch 'act-1963' of https://github.com/lsmall/Activiti
Small changes
Merge pull request #365 from xuhuisheng/ACT-2093

fix ACT-2093 use x to replace y
Merge with master
Merge branch '5-17-camel-initiator-identity' of https://github.com/aschrijver/Activiti
Small change
ACT-2096: Deadlock while concurrently finishing process instances on MSSQL

Delete operations optimization is now disabled by default and can be enabled in config