removed some unused imports

Quote Maven related things in Readme.md

Add a pure grammar file;
Modify SimpleQuery.java

mv PureGrammar.jj to root to keep maven correct

Update PureGrammar for further dev;
Support multi delete;

Further work:
  Use JUnit to write tablename finder & test code
  Modify the grammar file to fit mysql sql statement

Update PureGrammar.jj

Update select/delete in puregrammar.jj

update two jj files

update jj file structure

update JSqlParserCC.jj
add sections guide in JSqlParserCC.jj