Drop Generation.canonical_pokedex.

Generation VI doesn't have a canonical pokedex (it has three). We don't
use this anywhere and as far as i can tell we never have. We can revive
it in another form if and when we find we need it.

Conflicts:
	pokedex/data/csv/generations.csv
	pokedex/db/tables.py

pokedex/data/csv/generations.csv

@@ -1,7 +1,7 @@
-id,main_region_id,canonical_pokedex_id,identifier
-1,1,2,generation-i
-2,2,7,generation-ii
-3,3,4,generation-iii
-4,4,6,generation-iv
-5,5,8,generation-v
-6,6,12,generation-vi
+id,main_region_id,identifier
+1,1,generation-i
+2,2,generation-ii
+3,3,generation-iii
+4,4,generation-iv
+5,5,generation-v
+6,6,generation-vi

pokedex/db/tables.py

@@ -862,8 +862,6 @@ class Generation(TableBase):
         info=dict(description="A numeric ID"))
     main_region_id = Column(Integer, ForeignKey('regions.id'), nullable=False,
         info=dict(description="ID of the region this generation's main games take place in"))
-    canonical_pokedex_id = Column(Integer, ForeignKey('pokedexes.id'), nullable=False,
-        info=dict(description=u"ID of the Pokédex this generation's main games use by default"))
     identifier = Column(Unicode(16), nullable=False,
         info=dict(description=u'An identifier', format='identifier'))
 
@@ -2273,8 +2271,6 @@ Experience.growth_rate = relationship(GrowthRate,
     backref='experience_table')
 
 
-Generation.canonical_pokedex = relationship(Pokedex,
-    backref='canonical_for_generation')
 Generation.versions = relationship(Version,
     secondary=VersionGroup.__table__,
     innerjoin=True)