CLI Refactor

[NicEastvillage]

This PR refactors our CLI

Notable changes for usage:

• cgaal solver and cgaal global has been merged to cgaal check
  • The flag --global will make cgaal use the global algorithm (and conflicts with --search-strategy=)
• Required arguments are now positional
  • E.g. cgaal check mymodel.lcgs myquery.atl instead of cgaal solver -m mymodel.lcgs -f myformula.atl
• Some flags have been renamed
• Some environment variables have been removed

Notable internal changes:

• Argument parsing have been moved to args.rs
• File loading has been moved to load.rs
• Arguments are stored in CliOptions struct
• Removed duplicate code caused by having to handle both LCGS vs JSON models
• Reduced the use of std::exit, using Results instead

More refactoring is possible. E.g. update clap and use the new derive pattern (essentially the cli is generated from a struct like CliOptions), search strategy dispatching still cause a lot of duplicate code, but I will stop here before the PR gets too big.

[falkecarlsen]

Nice, some comments om SEMVER and args

[falkecarlsen]