Started a new approach inspired by the State(305) design pattern
New version is working nicely so far - just got running totals to sort out

...and probably some more refactoring
Got running total working
Renamed Frame2 to Frame etc and removed all the old horrid code
A few bits of tidying up
Extracted a couple of methods to make ProcessRolls clearer
Gave FrameNumber a private setter and renamed a couple of enum values
The app now presents a list of predefined rolls to choose from
The console app now highlights the frame numbers, rolls and running totals