logLevel as server setting, logger config page, re-scan audiobook option, fix embedded cover extraction, flac and mobi support, fix series bookshelf not wrapping

server/utils/constants.js

@@ -9,4 +9,14 @@ module.exports.ScanResult = {
 module.exports.CoverDestination = {
   METADATA: 0,
   AUDIOBOOK: 1
+}
+
+module.exports.LogLevel = {
+  TRACE: 0,
+  DEBUG: 1,
+  INFO: 2,
+  WARN: 3,
+  ERROR: 4,
+  FATAL: 5,
+  NOTE: 6
 }