Adding tests for AsyncExecutor + support for executors nodes going down and jobs being picked up by others
Merge branch 'master' of https://github.com/Activiti/Activiti

# By Tijs Rademakers (2) and nosovp (1)
# Via Tijs Rademakers
* 'master' of https://github.com/Activiti/Activiti:
  New version of Activiti Modeler (Angular JS) and upgraded to 5.17.0
  Manual fix for pull request 476
  Update of joda-time library (from 2.1 to 2.6) to support timezone changes in some countries, e.g. in Russia.