Add IP bans

Users can be banned by IP address now, either by singular IP or in an IP
range. If they are banned and attempt to post, they will be met with a
"you are banned until X date" screen.

There are a few loose threads with this, and IP bans may be obsolete if
I decide to go the accounts-required-for-posting route. But I think this
is a good start for 4chan style posting.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

board/admin.py

@@ -1,6 +1,6 @@
 from django.contrib import admin
 from django.utils.safestring import mark_safe
-from board.models import Board, Post, ReportReason, ReportRecord
+from board.models import Ban, Board, Post, RangeBan, ReportReason, ReportRecord
 
 
 @admin.register(Board)
@@ -45,3 +45,13 @@ class ReportRecordAdmin(admin.ModelAdmin):
         html += f"<p>{obj.post.text}</p>"
         html += "</div>"
         return mark_safe(html)
+
+
+@admin.register(RangeBan)
+class RangeBanAdmin(admin.ModelAdmin):
+    pass
+
+
+@admin.register(Ban)
+class BanAdmin(admin.ModelAdmin):
+    pass