- updated/improved discussion engine: it needs additional fine-tuning
  though but I think this is stable enough for public consumption and
  real-life testing.
   ==> a first big step towards a flexible comment engine.

IMPORTANT:
  - Required theme updatins:

    UnConeD: check your $theme->controls() as I added a very, very
             dummy implementation

  - Required database updates:

    alter table users modify mode tinyint(1) DEFAULT '' NOT NULL;
    alter table comments change sid lid int(6) DEFAULT '0' NOT NULL;
    alter table comments add link varchar(16) DEFAULT '' NOT NULL;
    update comments set link = 'story';