NumberRange changes for revisions 30018:30019

Applied a suggestion from jgarnett. This is the same declaration pattern than in the standard Collections.min(Collection) JDK method and can not be applied in a different way. Identical parameters are also provided in reply to a question on StackOverflow (page read on February 13th, 2013), so we could copy-and-paste the same content than this commit from there.

Command line:

svn diff --extensions "--unified --ignore-space-change --ignore-all-space --ignore-eol-style" -r29987:30019
Revision 30018Revision 30019
public class NumberRange extends Range {
public class NumberRange<T extends Number & Comparable<? super T>> extends Range<T> {