Merge branch 'bug-8753-mitk-micro-services-2'

• bug-8753-mitk-micro-services-2: Added snippet for singleton service use. Use more generic way to set-up include and lib paths for snippets. Check for absolute paths of snippet source files. Fix retrieving symbol handles from the executable. Minimize locking of code to avoid recursive locks. Fixed ServiceRegistration copy constructor. Fixed bad any_cast. Use consistent naming for "unlocked" methods. Avoid recursively locking non-recursive mutexes.