Chi middleware and bug fixes

Merged a few pull requests.

• Chi server allows for middleware functions
• Fix a bug in operations which have only cookie parameters
• Detect non-string enums and report an error instead of crashing

time/date binding and deepObject fixes

Fixed several issues with binding time and date parameter values.

• type aliases now bind correctly, used to be silently ignored
• deepObject marshaled structs now unmarshal time without dropping down to date granularity
• Added a lot of tests so this doesn't regress.

BaseURLs and config files

• Server side generation now supports a BaseURL for registering paths. It's prepended to the paths in the OpenAPI spec, so you can host the server behind a prefix router, and still have Echo and Chi register the full path for proper path resolution
• Command line arguments were getting unwieldy. They're still supported as-is, but you can optionally replace them with a configuration file now.

Unsigned int fields and bug fixes

• Schemas can use unsigned ints. It's not supported in swagger, but also doesn't break valid swagger
• fixed code generation error in client response parsing which generated broken 404 handlers

Merged miscellaneous PR's

• x-go-type extension for defining custom types names
• some error message fixes
• load swagger spec from URL

Bug fixes

• Fix type generation for path parameter lists
• Fix additional properties handing for allOf schemas

Chi code update, and bug fixes

• Chi callbacks now more closely resemble those in Echo, with args being passed in similarly

External reference support and bug fixes

• External references now work, and an '--import-mapping' parameter to oapi-codegen specifies how to find their generated Go code
• Merged several bug fixes.

Thanks everyone for your pull requests.

Bug fixes

• I merged an number of bug fixes submitted via pull requests, thank you for your contributions.

Sorry for the long delays these days, things are hectic.

Bug fixes and improvements

• Various bug fixes, particularly in date parsing and basePath handling
• By default, unused component schemas don't produce Go types anymore.