Enforce unique AuthServicesInfo (#618)

Alter user field to OneToOneField
Migration to enforce uniqueness pre-change
Migration to ensure all users have an AuthServicesInfo
Receiver to automatically create one upon user creation
Replace AuthServicesInfo.get_or_create with get
Prevent deletion of AuthServicesInfo from admin site
Remove add and delete permissions from model.

Get character names in chunks on corpstats update to prevent HTTP400 when requesting >350(ish) names

Include corpstats docs.
Update settings docs.

corputils/managers.py

@@ -9,7 +9,7 @@ class CorpStatsQuerySet(models.QuerySet):
         if user.is_superuser:
             return self
 
-        auth = AuthServicesInfo.objects.get_or_create(user=user)[0]
+        auth = AuthServicesInfo.objects.get(user=user)
         try:
             char = EveCharacter.objects.get(character_id=auth.main_char_id)
             # build all accepted queries

corputils/models.py

@@ -89,7 +89,7 @@ class CorpStats(models.Model):
         return [name for id, name in self.members.items()]
 
     def show_apis(self, user):
-        auth = AuthServicesInfo.objects.get_or_create(user=user)[0]
+        auth = AuthServicesInfo.objects.get(user=user)
         if auth.main_char_id:
             try:
                 char = EveCharacter.objects.get(character_id=auth.main_char_id)