refactor server_export
refactor the code style of server_export
fix the undefined error
Merge branch 'master' of https://github.com/phpmyadmin/phpmyadmin into server_refactor2
fix undefined variable: multi_values
rename server_export.lib.php to display_export.lib.php due to it works for server and database, table level export
Merge pull request #531 from xmujay/server_refactor2

refactor server_export