8207690: Parsing API for classpath and similar path strings

[Roger Riggs]

Please review the API and implementation of an API to parse Path strings.
Two methods are added to java.nio.file.Paths to parse a string using the 
path separator delimiter
and return either List<String> or List<Path>.  Empty path elements are 
ignored.

For compatibility with current URLClassPath behavior the internal 
implementation handles
replacement of empty paths.

Webrev:
http://cr.openjdk.java.net/~rriggs/webrev-8207690_parsing_api_for_classpath_and_similar_path_strings/

CSR:
   https://bugs.openjdk.java.net/browse/JDK-8208208

Thanks, Roger