..F....... [ZBXNEXT-1583] Implement "Graph prototype" and "Simple graph prototype" screen element types: 
- Update screenedit.php to handle "max_columns".
- Update flickerfreescreen.js to support new screen element types.
- Add new screen element types to screens.inc.php.
- Add new constants SCREEN_SURROGATE_MIN_COLUMNS and SCREEN_SURROGATE_MAX_COLUMNS to defines.inc.php.
- Update configuration.screen.constructor.edit.php to handle both new screen element configurations.
- Update CScreenBuilder.php to recognize new screen element types.
- Implement new screen element output classes CScreenLldGraph and CScreenLldSimpleGraph. Both classes extend CScreenLldGraphBase class.