Support multiple HTTP ranges in a request

Currently Nexus Repo 3 only supports HTTP GET requests that contain a single range in the "range" header.

curl -v -r 10-20 http://localhost:8081/repository/maven-public/ant/ant/1.6/ant-1.6.pom

The above results in an HTTP 206 (partial content) response, as expected, and 11 bytes sent back

However if multiple ranges are used all content is always returned:

curl -v -r 10-20,30-40 http://localhost:8081/repository/maven-public/ant/ant/1.6/ant-1.6.pom -v

The above gets a 200 response, and all content is returned.

For effective retrieval of large files with tools like zsync (http://zsync.moria.org.uk/) it's important to be able to retrieve multiple parts in a single HTTP request.