Load/save filter settings from text format instance instead of globally

Table style and HTML mode on/off settings were loaded from global var table via variable_get().
Filter settings should be loaded/saved from the text format filter object. This way, each instance of tables filter can be configured different for each text format where is used. If no filter settings are given, same defaults are still loaded from variables table.
Also removed unnecessary fieldset element in settings Form API definition.
Now you can specify different table style in each text format.

NOTE: Correct patch is in comment #1.

Related docs:
http://api.drupal.org/api/drupal/modules%21filter%21filter.api.php/funct...
http://api.drupal.org/api/drupal/modules%21filter%21filter.api.php/funct...