Throws logic_error if these modifiers are used in the top level

This can be overridden by a newly introduced boolean argument. Including the return channel was causing problems e.g. when propagating the DataValidity flag.

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

Added preliminary support for bidirectional variables. There are still some known issues, e.g. concurrent updates can still lead to race conditions. This will be addressed soon.

Updated to use the new ReadAnyGroup instead of the old readAny function. Some tests are still hanging or failing (mostly due to shutdown issues)

Proper implementation of move constructors and move assignment operators for all module types (including tests for the assignment operator)

Fixed a bug that sometimes variables were read (resp. written) in groups despite they were outputs (resp. inputs). This was happening with device variables since they are bi-directional. Now no longer the information from the accessor is used whether this variable is readable or writeable, but the information from the VariableNetworkNode which direction this variable should have.

fixed connectTo() so it now uses the dynamic/virtual model and thus obeys e.g. eliminated hierarchies etc.

Make Module::connectTo() no longer a template, since a virtual function can anyway not be overridden with a different return type... (c.f. the comment in the deleted code)

obey the eliminate hierarchy flag when using the () and [] operators of modules (and thus also when using connectTo())

made Module::connectTo() compile-time polymorphic, to allow special modules with operator() returning a different type.

Changed Module::readAll() to read all push-type variables first, to make sure that poll-type variables are up-to-date upon return

moved group read/write and []/() oprerators from the VariableGroup class into the Module class, to make the functionality also available in ApplicationModules

Changed Module::connectTo() to accept also temporary module objects, e.g. as returned by findTag(). As a consequence, the operators [] and () of the modules had to be changed to const.

- allow setting the "eliminateHierarchy" flag in the constructor of a module

This is an interface change which was done in an incompatible way!

Rebased the ScalarAccessor and ArrayAccessor classes onto the mtca4u::NDRegisterAccessorBridge class.
Known problems present: code compiles but tests do not run