chore(variable): Exclude byte types from query

- the variable instance query does not select variable instances with type
  equals 'bytes'
- Furthermore, the values of the selected variable instances will be
  fetched initially to prevent NEPs later

related to CAM-780
fix(engine): Set parent activityInstanceId

- in the case of parallel multiple subprocess containing a parallel
  gateway the running execution had the wrong activity instance id
- now the running execution has as activity instance id the activity
  instance id of the sub process (i.e. the parent activity instance id)

related to CAM-780
feat(variable): Load variable instances in cockpit

- In cockpit the current variable instances of the selected process
  instance are shown.
- On click on a bpmnElement or on an activity instance node only the
  variable instances for the current selection will be shown.
- Improve layout of cockpit
- Clean up some directives

related to CAM-780
Merge branch 'master' of github.com:camunda/camunda-bpm-platform