Container::clear()/free()++, bugfixes ...

- OZ_DYNAMICS fixed
- ozCore
  * aFree doesn't set elements to nullptr any more
  * Container::clear()/free() ++, more consistent
  * String updates Alloc::amount & co.
- ui
  * selection/drag fixes
- client
  * buildMenu visibility fixed, ozUIEnableBuild -> ozUIBuildMenu
  * MECH camera position fixed
- tests
  * mono test removed