Add preliminary jobs's interfaces

Creating:
jobsResource.getJobByName(providerName, jobName)
    provider: jobProvider.getJobInitialPath(jobName)
job.createJobExecution(params)
    provider: jobProvider.createExecution(params)

Querying state (list):
jobsResource.searchJobExecution(params)
    provider: jobProvider.getExecution(jobName, id)
              (for each execution in created or running state)

Querying state (single execution):
jobsResource.getJobExecution(providerName, jobName, jobExecutionId)
    provider: jobProvider.getExecution(jobName, id)
              (if the execution is in created or running state)

Cancelling job:
jobsResource.getJobExecution(providerName, jobName, jobExecutionId)
        .requestCancellation()
    provider: jobProvider.getExecution(jobName, id)
              (if the execution is in created or running state)