HGTD Digi: SurfaceChargeGenerator and FrontEndTool
Light at the end of the tunnel...
Adding two more tools for the HGTD digitization and "activating" use of the charge generator in the digi tool.
The FrontEndTool is "empty" for now, here @tawang will add the signal pulse generation later. Putting everything in though, we can at least test the full chain then and start configuring everything.