Updated docs: use .wid instead of .conf
 - updating out-of-date test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 - fixing out-of-date test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
JBPM-3913: Exception handling and improved work item documentation

- Added an exception handling chapter (documentation) and examples
- Rewrote the "Domain-Specific Processes" chapter
- Added (exception handling) examples that are referenced in the documentation
- Moved certain sections to the Designer and Eclipse plugin chapters