[jaring] lib.Jaring: add variable _mod_home and _mod_main.
[jaring] home/layout.css: change image path to absolute path.
[jaring] lib.Jaring: Add option to set query from two or more tables.
[jaring] System.Profile: remove read.php, use db relationship option.
[jaring] Replace db_rel.links with db_rel.conditions.
[jaring] System.Profile.User: replace read.php with db_rel options.
[jaring] lib.Jaring: add relationship option for search and order.
[jaring] System.Group.User: replace read.php with internal db_rel option.
[jaring] System.User: fix read options.
[jaring] lib.Jaring: refactoring.

* implode_with_circumfix: new function.
* Replace multi-line comment with single.
* db_create: new function.
* db_get_connection: removed.
* db_execute_script: new function.
* Replace Jaring with self.
* request_read_populate_relationship: new function.
[jaring] Change cookies key name.
[jaring] lib.Jaring.get_last_insert_id: removed.
[jaring] Jaring.request_read_populate_relationship: add parameter query.

* Change conditions to use only value.
[jaring] Fix db relationship conditions.

* System.Profile.UserNon
  - use db relationship operands
  - remove read.php.
[jaring] init: surround with try-catch.
[jaring] Add icon for reference.
[jaring] Fix menu content single.
[jaring] db: add group User.
[jaring] execute_script: catch error when executing statement.
[jaring] check if field exist before pushing to array.