Require e.g. when needing to report an exception programmatically

The previous implementation using the mutex had two issues:

1. The mutex was locked in a different thread than unlocked (DeviceModule constructor vs. handleException() thread). This results in undefined behaviour.
2. The boost::shared_mutex::lock_shared() function is not an interruption point, so applications did not terminate while waiting for initial values. (boost::latch::wait() is an interruption point.)

Just use enableDebugDataLoss() to enable debug output.

- testCircularDependencyFaultyFlags now uses modern AC without defining CS module and overriding defineConnections()

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Circular dependency detection: Outputs which are pogrammatically set to faulty are treated like external inputs.

- Implemented but not tested yet
- All existing tests passing

* Not implemented yet. Currently always return false.
* Test exists and compiles, but is failing due to the missing implementation.

Paths starting with "/" will be stripped of the leading slash now. Empty paths (or a single slash) will be interpreted to refer to the Module itself and hence return *this.

This logic is otherwise ofter required in code which uses submodule().

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

Co-authored-by: Jens Georg <jens.georg@desy.de>

Prints a clear message if a circular dependency of initial values exists.