Getting rid of `new File(URL.getPath()).toURI()`

@jansupol Earlier this year you had to rework my NIO2 optimizations in Jersey due to problems with Windows path names. We found out that the original cause was not the `Path` class itself, but Jersey's use of `URL.getPath()`. In https://bugs.openjdk.org/browse/JDK-8314511 you claimed that you abstain from using Team OpenJDK's solution (`URL.toURI()`) because of *performance* reasons. Due to that I openend https://bugs.openjdk.org/browse/JDK-8321591 and checked the Jersey source code. In fact, I could not find a proof for a notable performance loss in Jersey's critical path, nor any other good reason for keeping `new File(URL.getPath()).toURI()`. As @AlanBateman explained several times, it is just a question of time until Jersey will run into a runtime fault as that code line will definitively fail with blanks in spaces (which is quite typical on Windows thanks to the `Program Files` folder for example). Hence I would kindly ask you to work with me to identify the actual reason why you still keep that "broken" code (and the risk of runtime failure), *or* to identify changes needed in OpenJDK to overcome your pretended performance shortcomings. Thanks! :-)