Returns default docking theme for Visual Manager.
This function returns one of the following values:
- BCGP_SDT_VS2005 - docking markers have VS 2005 look.
- BCGP_SDT_VS2008 - docking markers have VS 2008 look.
- BCGP_SDT_VS2010 - docking markers have VS 2010 look.
- BCGP_SDT_VS2012 - docking markers have VS 2012/2013/2015 look.