added general event handling to DrawingHandler

FocusTerra/.vs/FocusTerra/v16/.suo

...ra/v16/ipch/AutoPCH/13073c15335d2976/DRAWING_HANDLER.ipch

...pch/AutoPCH/2497ca4debdda90c/SLIM_BLOCKCHAIN_HANDLER.ipch

...sTerra/v16/ipch/AutoPCH/3b7f66ca6222ba83/GUI_HANDLER.ipch

FocusTerra/FocusTerra/x64/Release/FocusTerra.iobj

FocusTerra/FocusTerra/x64/Release/FocusTerra.ipdb

FocusTerra/FocusTerra/x64/Release/FocusTerra.log

.../FocusTerra/x64/Release/FocusTerra.tlog/CL.command.1.tlog

...rra/FocusTerra/x64/Release/FocusTerra.tlog/CL.read.1.tlog

...ra/FocusTerra/x64/Release/FocusTerra.tlog/CL.write.1.tlog

...a/FocusTerra/x64/Release/FocusTerra.tlog/link.read.1.tlog

FocusTerra/FocusTerra/x64/Release/gui_handler.obj

...sTerra/FocusTerra/x64/Release/slim_blockchain_handler.obj

FocusTerra/FocusTerra/x64/Release/vc142.pdb

FocusTerra/x64/Release/FocusTerra.exe

FocusTerra/x64/Release/FocusTerra.pdb

include/drawing_handler.hpp

include/gui_handler.hpp

include/slim_blockchain_handler.hpp

src/drawing_handler.cpp