fix(rest): add workaround for old jackson dependency

- WAS uses a old jackson version which doesn't support the
  EXTERNAL_RESOURCE annotation
- dirty JSON workaround to compile on WAS again

related to #CAM-2628
chore(rest): use same configured ObjectMapper instance in FilterDto

related to #CAM-2628
fix(rest): throw generated expceptions
chore(engine): refactor test to be deterministic
chore(engine): code cleanup / test refactoring

related to CAM-2629
chore(parent): set javadoc version to fix issues with 2.10
 chore(release): Prepare release: set version to 7.2.0-alpha5
 chore(release): Prepare next development version: 7.2.0-SNAPSHOT
fix(engine): iomapping for multi instance constructs

- execute input mappings such that local variables are created for every
  instance
- disallow output mappings as they require a larger refactoring of multi
  instance tasks (see CAM-2787) and have also questionable semantics
  because output mappings may override each other

related to CAM-2338
fix(engine): io mapping for events

- intermediate and end events
- throw parsing error for start and boundary events
- throw parsing error for event subprocesses

related to CAM-2400
fix(engine): propagate error that is thrown from event subprocess

- fixes ErrorPropagation and in particular the discovery of the execution
  responsible for executing boundary error events

related to CAM-2398
chore(engine-rest): change POST /task/{id}/comment to accept JSON

related to CAM-2402
fix(engine): fix infinite job creation caused by asyncAfter

related to CAM-2518
chore(jobexecutor): no rollback on OptimisticLocking

Do not rollback the transaction in case jobAcquisition rolls back with
an optimistic locking exception. Instead, simply remove job from list of
acquired jobs.

related to #CAM-2805
fix(engine-tests): replace direct joda time reference
feat(engine): extend supported async elements

-- asyncBefore, asyncAfter, exclusive are now available for:

- Intermediate Throw Events
- Intermediate Catch Events
- Start Events
- EndEvents
- Manual Task
- Exclusive Gateways
- Inclusive Gateways
- Event-Based Gateways (asyncAfter is not supported at the moment)

Related to: #CAM-2723
feat(rest): add itemCount query param and property to filter queries

related to #CAM-2801
fix(rest): annotate getter not field to work with WAS jackson version

related to #CAM-2801
feat(engine): 1st lvl cache reuse with exclusive jobs

Reuse the 1st level DbEntityCache for sequences of asynchronous
continuations executed by the same thread. (exclusive jobs).

Improves performance since the cache is not discarded when the command
context is flushed but reused by the next command.

Cache reuse is disabled by default, can be enabled by setting
"isDbEntityCacheReuseEnabled" to true.

Caches instances polymorphic types (such as JobEntity as super class of
MessageEntity and TimerEntity) under a common key.

related to CAM-2763
chore(rest): align path to create task comment with most resources

- cause the REST API mainly uses a separate /create path on a resource
  to create a new instance we should stick to it also for task
  comments

related to #CAM-2402