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.

Fixed getCurrentVersionNumber() and setCurrentVersionNumber() so they always get/set the version number of the ApplicationModule and not e.g. of a VariableGroup.

bidirectional variables: pass on version numbers in modules from the last blocking read on to any write operations, to resolve conflicts of concurrent variable updates properly

Include descriptions of the owning Module in the descriptions of each process variable to make them more complete.

We have a visitor now for generating
 - the XML
 - the Module's dot graph
 - the textual dump of the VariableNetwork
 - the dot graph of the VariableNetwork

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

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

- removed the no-longer-necessary optional argument of findTag() - use flatten() instead

Fixed some more problems with the move sematics of EntityOwner/Module. Re-registration at the owner was missing and some things were done in the wrong place. Also the move assignment is now back again.

put the move constructor and move assignment-operator into the EntitiOwner base-class and inherit them

This reverts commit 7287c4b4.

revert last commit, cascading ApplicationModules should be avoided instead (and should be prevented in future)

added function to obtain the qualified name of the variable, including the hierarchy path. not yet used.

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

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

added function to flatten teh hierarchy, renamed eliminateHierarchy() into setEliminateHierarchy() for better clarity

added preliminary support for tags to application variables which can be searched for and used to generate virtual modules

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