feat(karaf-commands): camunda specific commands to the karaf console

Hi, 

We created a simple extension to the karaf console to make it easier to check the actual state of the engine from the karaf console.

```
karaf@default> help camunda
COMMANDS
        camunda:activity-list       List activities
        camunda:deployment-list    List camunda deployments.
        camunda:execution-list      List process executions by process definition.
        camunda:export-diagram      Export definition of a diagram
        camunda:instance-list       List process instances of a specific process definition.
        camunda:process-list        List process definitions.
        camunda:task-list           List tasks for a specific process definition.
        camunda:variable-list       List variables on a specific instance.
```