Add Japanese generation names, and fix Gen VII

Add Japanese translations of the generation names, thanks to @SethETaron. I think this marks our first unofficial Japanese translation. 🎉

Also, fix some issues with Gen VII:

* generation names were missing for every language
* the identifier was incorrect — it was sun-moon instead of generation-vii

Fixes #250, #251, and #252.

pokedex/data/csv/generation_names.csv

@@ -1,19 +1,36 @@
 generation_id,local_language_id,name
+1,1,だいいっせだい
 1,5,Génération I
 1,6,Generation I
 1,9,Generation I
+1,11,第一世代
+2,1,だいにせだい
 2,5,Génération II
 2,6,Generation II
 2,9,Generation II
+2,11,第二世代
+3,1,だいさんせだい
 3,5,Génération III
 3,6,Generation III
 3,9,Generation III
+3,11,第三世代
+4,1,だいよんせだい
 4,5,Génération IV
 4,6,Generation IV
 4,9,Generation IV
+4,11,第四世代
+5,1,だいごせだい
 5,5,Génération V
 5,6,Generation V
 5,9,Generation V
+5,11,第五世代
+6,1,だいろくせだい
 6,5,Génération VI
 6,6,Generation VI
 6,9,Generation VI
+6,11,第六世代
+7,1,だいななせだい
+7,5,Génération VII
+7,6,Generation VII
+7,9,Generation VII
+7,11,第七世代

pokedex/data/csv/generations.csv

@@ -5,4 +5,4 @@ id,main_region_id,identifier
 4,4,generation-iv
 5,5,generation-v
 6,6,generation-vi
-7,7,sun-moon
+7,7,generation-vii