Merge branch '189-mailinglist-member-selection' into 'master'

Add better member selection to mailinglists admin

Closes #189

See merge request !200

website/mailinglists/admin.py

 from django.contrib import admin
+from members.models import Member
 
 from .models import ListAlias, MailingList, VerbatimAddress
 
@@ -13,4 +14,6 @@ class ListAliasInline(admin.TabularInline):
 
 @admin.register(MailingList)
 class GeneralMeetingAdmin(admin.ModelAdmin):
+    model = Member
+    filter_horizontal = ('members',)
     inlines = (VerbatimAddressInline, ListAliasInline)