multiple sample cases.
Merge pull request #43 from pfctgeorge/multiple-sample-cases

add support to multiple sample cases.
add checker for contest archive ZIP.
update .gitignore.
remove redundant setting constants.
use AppExceptionUtil to validate file is not null.
modify exception message and file type validation for reusing.
reuse ZipDataChecker.
throw exception when no test data file in problem information directory.
fix coding style issue
fix unit tests.
remove the limit for problem information directory name.
update .gitignore.