Introduce an order column for version groups

Some code in spline-pokedex orders by `id`, which has worse consequences
than it may seem (e.g. instead of defaulting to most recent games, the
comparifier defaults to XD). This is the first step to fixing that.

pokedex/data/csv/version_groups.csv

@@ -1,14 +1,14 @@
-id,generation_id,pokedex_id
-1,1,2
-2,1,2
-3,2,3
-4,2,3
-5,3,4
-6,3,4
-7,3,2
-8,4,5
-9,4,6
-10,4,7
-11,5,8
-12,3,4
-13,3,4
+id,generation_id,pokedex_id,order
+1,1,2,1
+2,1,2,2
+3,2,3,3
+4,2,3,4
+5,3,4,5
+6,3,4,6
+7,3,2,8
+8,4,5,10
+9,4,6,11
+10,4,7,12
+11,5,8,13
+12,3,4,7
+13,3,4,9

pokedex/db/tables.py

@@ -1587,6 +1587,8 @@ class VersionGroup(TableBase):
         info=dict(description=u"The ID of the generation the games in this group belong to."))
     pokedex_id = Column(Integer, ForeignKey('pokedexes.id'), nullable=False,
         info=dict(description=u"The ID of the regional Pokédex used in this version group."))
+    order = Column(Integer, nullable=True,
+        info=dict(description=u"Order for sorting. Almost by date of release, except similar versions are grouped together."))
 
 class VersionGroupRegion(TableBase):
     u"""Maps a version group to a region that appears in it."""