Changed IAssemblyLoaderEngine.LoadBytes to LoadStream
- Optimized for CoreCLR scenarios
- Desktop CLR will convert to byte[]
React to new Roslyn API
Refactor command-line parser

1. Add CommandOptionType in CommandLineApplication parser
2. One option can have multiple values in CommandLineApplication now
3. Add helper methods that generate help information in
CommandLineApplication
4. Replace all usages of CommandLineParser with CommandLineApplication
parser
Add support for help options of subcommands

1. Merge CommandLineApplication and CommandInfo into one class to allow a
more consistent recursieve processing
2. Help options are treated specially because they are different from
common options (help options invoke actions)
3. Show help information when find invalid options/subcommands