Add size method to Methcla::Request
Fix compile error

The SystemError exception class doesn't exist anymore.
Compile dummy driver only for test target
Use API function instead of including version header

Include version header only in API.cpp
Add (de)interleave methods to MultiChannelBuffer
Handle all arguments in Methcla_Engine constructor
Add folder references for plugins and src to Methcla project
Use std::unique_ptr instead of pointer members

Make sure that worker is constructed before and destroyed after node
map. Synths might schedule commands in their destructor and the worker
must still be around.
Initialize pointer to worker in member initializer
Update ChangeLog from pro/develop
Replace boost intrusive list by linked list implementation for node tree

Make sure that groups free their children and freed synths that are
still referred to by asynchronous commands cannot access their parent.
Add freeAll API command for freeing all nodes in a group