qemu: use generalized virDomainJobData instead of qemuDomainJobInfo

qemu: use generalized virDomainJobData instead of qemuDomainJobInfo

This patch includes:
* introducing new files: src/hypervisor/domain_job.c and src/hypervisor/domain_job.h
* new struct virDomainJobData, which is almost the same as
  qemuDomainJobInfo - the only differences are moving qemu specific
  job stats into the qemuDomainJobDataPrivate and adding jobType
  (possibly more attributes in the future if needed).
* moving qemuDomainJobStatus to the domain_job.h and renaming it
  as virDomainJobStatus
* moving and renaming qemuDomainJobStatusToType
* adding callback struct virDomainJobDataPrivateDataCallbacks
  taking care of allocation, copying and freeing of private data
  of virDomainJobData
* adding functions for virDomainJobDataPrivateDataCallbacks for
  qemu hypervisor
* adding 'public' (public between the different hypervisors) functions
  taking care of init, copy, free of virDomainJobData
* renaming every occurrence of qemuDomainJobInfo *info to
  virDomainJobData *data

Signed-off-by: Kristina Hanicova <khanicov@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>