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.
In order to support PHP7 and Ubuntu 16.04, there must be some changes to make it runs properly.
The install script added php7 and mysql 5.7, newer v8js packages and supports, adjusted some config files.
Also used new way to detect install args, and change tab to 4-char-long space char.
BREAKING CHANGE: This branch can only be used for PHP7, and Ubuntu 14.04 users shouln't execute this script.
The last commit changed the installation script a lot, but made some mistakes on the genration of config.
It gens the $_svn_ourroot_password_ to $_svn_certroot_password_. Just fix it.
According to the version from @vfleaking, the judger_socket password and the our-root password is 32 chars long. Strengthen it.
There is also a *** space char on the end of a line. Kick it out.
Change the base Docker image to ubuntu16.04 and change the LAMP
packages to support PHP7.
BREAKING CHANGE: the packages which will be installed has changed.
