can replace Codegen and MetaGenerator classes. Provides a bit different cli interface
based on refactored pom from #541,
affects #349
```
usage: swagger <command> [<args>]
The most commonly used swagger commands are:
generate Generate code with chosen lang
help Display help information
langs Shows available langs
meta MetaGenerator. Generator for creating a new template set and configuration for Codegen. The output will be based on the language you specify, and includes default templates to include.
```
**generate** and **meta** commands have same as current cli options
