Since PHP 5.1.0 (when the date/time functions were rewritten), we need to specify the default timezone.
Otherwise the timezone will always set to UTC that may cause problem or cause confusion.
We set the default timezone to Asia/Shanghai. If you are not at the area of this timezone, you can change it manually.
Update base system to Ubuntu 18.04.
.htaccess file's session path changed correctly.
Add gnupg install choice, due to base system has no gpg support.
Set DEBIAN_FRONTEND to noninteractive in order to prevent tzdata stuck.
Change Dockerfile's verion and buanch checkout method, in order to save space.
Fix mysql conf when not restart service and the database can't import judger info.
Change install.sh, support PHP7.2, update libv8 repo to artful, with missing php-mbstring.
The old JDK distfile mirrors are deprecated, changed to official.sed modded to get the latest jdk8.
BREAKING CHANGE: Ubuntu 14/16 users shouln't execute this script, due to config files and packages not the same.
