Too many refactors in one:

- Allowed adding ephemeral(ish) views and functions
- Moved message_count to a concrete database field
- Moved most proxy logic to a stored procedure
- Moved database files around and refactored schema manager

PluralKit.Core/Models/PKMember.cs

@@ -22,6 +22,7 @@ namespace PluralKit.Core {
         [JsonProperty("proxy_tags")] public ICollection<ProxyTag> ProxyTags { get; set; }
         [JsonProperty("keep_proxy")] public bool KeepProxy { get; set; }
         [JsonProperty("created")] public Instant Created { get; set; }
+        [JsonProperty("message_count")] public int MessageCount { get; set; }
 
         public PrivacyLevel MemberPrivacy { get; set; }