Allow the engine to handle only certain definitions

In some cases it is convenient many Flowable engines to share a single database and tables set. But then it is possible the environment of each engine to not satisfy the requirements of each process definition, for example the engine instance environment may not contain/provide the required delegates (implementations of `org.flowable.engine.delegate.JavaDelegate`).

To overcome this inconvenience:
1. Develop a BPMN extension on process level, which to define process definition execution grouping;

2. Add in the engine configuration a parameter to define a list of process definition "groups" this engine instance to handle. The parameter should also allow definition of a list with exclusions, i.e. which process definitions the engine instance to **not** handle. The existence of both lists in the same configuration seems meaningless, except in the case the list definition allows wildcards or regular expressions. The allowance of wildcards and regular expressions in the lists should be further decided by the Folwable Engine development management;

3. Implement a filter in the engine's process definitions loading mechanism to load only the eligible (according to the engine configuration) definitions from the database;

4. Process definition eligibility description using process definition identifier (key) or name is out of scope. The eligibility of specific process definitions should be also defined using the "execution grouping" BPMN extension.

Note: This issue is based on the forum discussion http://forum.flowable.org/t/restrict-the-engine-to-handle-only-certain-definitions/245

Commencez par suivre la configuration du moteur et le mécanisme de chargement des définitions de processus décrits dans l’issue, puis examinez comment les extensions au niveau du processus BPMN sont représentées et lues. Clarifiez avec les mainteneurs le format de regroupement de l’exécution ainsi que les règles d’inclusion ou d’exclusion avant de modifier le code. C’est terminé lorsque les définitions éligibles sont chargées, tandis que les définitions non éligibles provenant de bases de données partagées sont ignorées, avec une couverture du comportement de configuration choisi.

Rédigé par le modèle d'indexation à partir du texte de l'issue.