add uuid method
add new constants
 Changes to be committed:
   (use "git reset HEAD <file>..." to unstage)

	new file:   src/main/java/org/apache/niolex/commons/util/Const.java
	modified:   src/main/java/org/apache/niolex/commons/util/DateTimeUtil.java
	new file:   src/test/java/org/apache/niolex/commons/util/ConstTest.java
	modified:   src/test/java/org/apache/niolex/commons/util/DateTimeUtilTest.java