Rework proxy based on original from https://github.com/mitre/HTTP-Proxy-Servlet/blob/master/src/main/java/org/mitre/dsmiley/httpproxy/ProxyServlet.java
Fix regex for https URLs with creds & switch to named capture groups for easier readability
Merge pull request #1449 from jimmidyson/jetty-proxyservlet

ProxyServlet doesn't support all methods (was: Delegate ProxyServlet to Jetty ProxyServlet)