conn.lib's CONN_3 reference symbol is inconsistent with other CONN_x

[Paul Sokolovsky]

CONN_2 is P?, CONN_4 is P?, but suddenly CONN_3 is K? . Obviously that's inconsistent and leads to weird component references if both CONN_3 and other connectors are used.

Besides, neither P?, nor K? are terribly intuitive. Most other packages call it JP?, which may be not too intuitive either, but at least kinda standard.

That's not the only inconsistency with conn.lib. For example, CONN_3 and bigger have 0.1" spacing between pins, but CONN_2 suddenly has 0.2", which requires bending schematic wires to connect to it in many cases. CONN_4, CONN_6, etc. are not filled rectangle, but CONN_5 is suddenly filled rectangle.

All the multitude of these "small" inconsistencies complicate work (more specifically, it makes quite hard to produce good-looking, professional-quality schematics), so thanks for considering fixing them.