rewrite the DemoPress.java
review.
Fix a link error of java doc.
refine test cases.
rename package  src/main/java/org/apache/niolex/network/packet into
src/main/java/org/apache/niolex/network/serialize
refine serialize package
refine the BasePacketWriter.java
set the socket buffer size to 64K
refine the SelectorHolder class.
refine the FastCore.