Add support of CORS in Undertow

Add support of Cross-Origin Resource Sharing (CORS) in Undertow.

CORS may be used to communicate client to perform cross-origin requests for resources that don't sit on the domain we performed original request against. E.g. site www.my-cool-domain.com uses some API hosted on www.cool-api.com domain. Then we can configure our server to provide CORS headers in HTTP responses from www.my-cool-domain.com which tells client that it is okay to load content from www.cool-api.com.

This could be implemented e.g. as an additional filter in Undertow.

Note that there already have been created some community implementations, see e.g.:

1. undertow-cors-filter on Github by Stijn de Witt
   • this implementation is created specifically for Underow creating custom HttpHandler implementation
   • is configured as a filter in standalone.xml of Wildfly/EAP
2. cors-filter by Vladimir Dzhuvinov
   • there is a Tomcat used in examples, although its usage seems to be quite universal as it implements javax.servlet.Filter interface
   • can be configured via web.xml of a deployment or via Java property file inside a deployment