InvalidityTracer and ConnectionMaker debug mode print now information
about circular networks

Constants (as generated by ApplicationModule::constant()) were causing a
logic_error if accessors of different types were using the same constant
(created with the same value and the same value type upon creation).
This is possible since the type passed to constant() does not have to be
the same as the type of the accessor.

This is now fixed by giving each constant a fully unique name, so every
accessor using a constant will be in its own little variable network.

- ControlSystemModule
- VirtualModule
- findTag
- excludeTag

and some related functions.

When writing special modules (e.g. the MicroDAQ module) it may be necessary to both override and call this function explicitly.

- Implemented but not tested yet
- All existing tests passing

This actually makes the implementation also easier and more efficient.

* add HierarchyModifyingGroup

* VirtualModule: allow nested oneLevelUp etc.; simplify implementation

This is achieved by properly setting the _owner of each VirtualModule (unless highest level).

The simplification comes from then being able to use getOwner() instead of keeping track of "grandparents", and from using createAndGetSubmodule() instead of implementing something similar again in findTagAndAppendToModule().

* DataLossCounter constructor now takes qualified path to trigger variable

- Initial values are sometimetimes only propagated in the first run of the main loops, not in prepare. If other modules are waiting for it they cannot enter their main loop. That's why all threads have to be started first, and only the it is waited for all of them to enter testable mode.

- removed ExceptionHandlingDecorator::setOwnerValidity()

- All accessors come up in exception state.
- Read-accessors increase counter in init phase

Assertion is gone, but tests still failing

  - EntityOwner has individual counters for both events
  - Adapted all instances of increment/decrementDataFaultCounter
  - Not changed getDataValidity() implementation yet
  - Tests failing

change declaration of 'decrementDataFaultCounter' in 'EntityOwner' to take a bool parameter and adjust rest of the code to it
implement 'decrementDataFaultCounter' in 'ApplicationModule' according to ticket #95 -> rewrite all outputs when 'faultCounter' goes from 1 to 0

Need to wait until the internal fan out threads have been launched and acquired the testable mode lock before continuing with app starting and testing to avoid race conditions.

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.