Mention TAP explicitly in reference manual

Signed-off-by: Frank Terbeck <ft@bewatermyfriend.org>
Add a detailed programexit section

Signed-off-by: Frank Terbeck <ft@bewatermyfriend.org>
Add a detailed plan section

Signed-off-by: Frank Terbeck <ft@bewatermyfriend.org>
Fix typo in manual

Signed-off-by: Frank Terbeck <ft@bewatermyfriend.org>