Add updater page, disabled by default

src/site/pug/admin_update.pug

@@ -0,0 +1,32 @@
+//- Needs {error} or {formattedLog, numberOfCommits, requiresDeps, requiresRestart}
+
+doctype html
+html
+	head
+		title Updater | Bibliogram
+		include includes/head
+	body.updater-page
+		if error
+			h1 Aw man.
+			div= error
+		else
+			h1 Bibliogram updater
+			if numberOfCommits > 0
+				div You are #{numberOfCommits} commits behind (most recent first):
+				div.commits
+					each line in formattedLog
+						div.commit
+							code.hash= line.hash
+							span.message= line.message
+				div
+					if requiresDeps
+						span.attention You must run #[code npm install] after pulling.
+					else
+						span No changes to dependencies.
+				div
+					if requiresRestart
+						span.attention You must restart Bibliogram after pulling.
+					else
+						span You do not need to restart Bibliogram after pulling.
+			else
+				div You are running the latest version. Hurrah!