Add option to use the Telemed US probes in CMakeLists of PlusBuild

Also add the package finder if the option is ON.
Add option to use the Telemed US probes in CMakeLists of PlusLib/src/DataCollection

Add what to do if PLUS_USE_TELEMED_VIDEO is ON :
- add source and header to the project
- search Telemed SDK and add the include directory to the project
- add definition -D_AFXDLL to the project
Keep only class skeletons for custom vtkPlusDevice (vtkTelemedVideoSource)
Got the build dir out of the git repo, so don't need .gitignore anymore
Update the DataCollection CMakeLists to correctly link the needed libraries
Permute include place to avoid error, and add content of former stdafx.h to vtkTelemedVideoSource.h
Fix linking problem by using link_directories() instead of TARGET_LINK_LIBRARIES()

In the DataCollection CmakeLists