Harmonise build process using submodules and CMake #155
Description
Current status
VTK and wxWidgets are included in the repo as submodules, but they are not automatically built when MoloVol is built.
Proposed change
When building MoloVol the build process should automatically build VTK and wxWidgets if necessary instead of relying on the developer to build each library manually. This will streamline the build process and make sure that library-linking works every time.