Add partial openSUSE/SLE support

Note that this is the first part of the support. A second part involves
dealing with the package names.

Among the changes:
 - add several functions to determine some distro-specific behavior (how
   to call usermod, if some features are available on the distro, etc.)
 - correctly detect openSUSE and SLE in GetOSVersion, and set DISTRO
   accordingly
 - new is_suse() function to check if running on a SUSE-based distro
 - use zypper to install packages
 - adapt apache virtual host configuration for openSUSE
 - some simple fixes (path to pip, mysql service name)

Change-Id: Id2f7c9e18a1c4a7b7cea262ea7959d183e4b0cf0

lib/databases/mysql

@@ -25,7 +25,11 @@ function configure_database_mysql {
         MYSQL=mysql
     else
         MY_CONF=/etc/my.cnf
-        MYSQL=mysqld
+        if is_suse; then
+            MYSQL=mysql
+        else
+            MYSQL=mysqld
+        fi
     fi
 
     # Start mysql-server