Fixed a slew of foriegn key import problems. #29

Curse's type_id was 0, which is bogus; this has been fixed by creating a
real ????? type.
Fourth-gen moves all had zero as a contest effect id, which was also
bogus.
Pokémon 494 and 495 were junk and have been scrapped entirely.
pokemon_form_groups's description column was too short.

pokedex's connect() now takes kwargs passed to sessionmaker().

A more major change: some tables, like pokemon, are self-referential and
contain rows that refer to rows later in the table (for example, Pikachu
evolves from Pichu, which has a higher id).  At the moment such a row is
loaded, the foreign key is thus bogus.  I solved this by turning on
autocommit and wrapping add() in a try block, then attempting to readd
every failed row again after the rest of the table is finished.  Slows
the import down a bit, but makes it work perfectly with foreign key
checks on.

pokedex/data/csv/pokemon_egg_groups.csv

@@ -645,8 +645,6 @@ pokemon_id,egg_group_id
 491,15
 492,15
 493,15
-494,15
-495,15
 496,15
 497,15
 498,15