[#47211625] Begin port of osm2iso to C++

Does not yet expect to compile.
[#47211625] Get ISOModel ForwardTranslator compiling
[#47211625] Comment out and annotate unused variables
[#47211625] Radiance / degrees bug fix

From @muehleisen
[#47211625] Updates to osm2iso.rb

From @muehleisen
[#47211625] Port updates to ForwardTranslator

from v84 to v86 from @muehleisen
[#47211625] Add comments to issues found by compiler

While porting osm2iso.rb to C++, some issues were found. I've annotated
them for @muehleisen to review.