New modes

The different tools that are built with or on top of VerCors, such as Alpinist, VeSUV and VeyMont, are internally implemented as modes of VerCors. To start:

• Add a mode in vct.options.types.Mode
• Add a flag that sets your mode in vct.options.Options
  • Also add any additional mode-specific options under your flag as children of that flag.
• Match your mode in vct.main.Main.runMode
• The outer shell of your mode should typically be an assembly of Stages, which is helpful in progress printing.
• Try to re-use stages in vct.main.stages if possible, otherwise implement your own logic as a hre.stages.Stage.