Dev mysql

+ I don't know whether github can choose certain files to merge and keep other files unmerged. 

+ Here is the file which **shouldn't be merged**.
 + README.md
 + src/test/java/net/baozi/jmysqlparser/test/*.java
 + .gitignore

+ And I don't know the other two files should be merged or not.
 + JSqlParser.jj --------          I changed the structure of this file and divide them into several sections.
 + PureGrammar.jj --------      I cleaned all java code and keep the grammar more clear, and add some TODO for mysql parser development.

+ squashed 11 commits into 1 commit.