fixed a potential invalid read/write error, access to object and its potential destruction was done in wrong order

 - Have a ZMQ push-type variable from a DOOCS-backed device that is NOT
   used as a trigger (otherwise the bug does not happen)
 - Connect that to an ScalarPushInput in an ApplicationModule
 - call readAnyGroup() from the ApplicationModule's main method

=> ReadAnyGroup.finalise() will cause an infinite recursion between
ExceptionHandlingDecorator::doReadTransferAsync and
TransferElement::readAsync because of wrong dispatching to the decorated
type

- add test for full exception handling

  DeviceModule and ControlSystemModule now do not take the optional prefix argument in their constructors any more. Use the [] operator instead to get the submodule.

- Add ExceptionHandlingDecorator and decorate all device variables with it.

move ApplicationModule::appConfig() to ModuleImpl::appConfig() so it can also be used from ModuleGroup

Implemented first part of #17: A HierarchyModifier can now be specified instead of the eliminateHierarchy boolean flag. No new functionality is yet added.

- reformatted source code

- added more comments
- need to catch exception by reference, else the message seems to be lost
- test if the message is correct
- test if device is really closed and opened again
- changed names of status variables in control system to match the general naming conventions

Do not try to make consuming control system variables bidirectional. It was running into an assertion and anyway makes no sense.

do not create TestableModeAccessorDecorator for unidirectional PVs with both directions enabled (was hitting an assert)

- treat the two directions of bidirectional variables properly in testable mode (i.e. as individual variables with each one counter)
- fix a data race in testable mode in case a bidirectional variable rejected a value (was not holding a required lock)

fixed bidirectional direct application to control system connections (without any FanOut in between)