There is subfolder in the uploaded data archive file, we can now process it.
We will move files in the subfolder out to the data rootdir of current problem.
If you have some data archives with subfolder, don't need to repack them manually.
In order to support PHP7, change the way to operate database. PHP7
removed the mysql extension, so the old way to operate database is
not usable. This commit use a new way to operate database.
BREAKING CHANGE: the way to operate database has changed.