improved library scan speeds, added library manager component

-libraries tab now opens a library manager
-choose library directory, manually soft scan and rescan
-batched db queues
-mp3 header-based duration extraction

frontend/wailsjs/go/library/Library.d.ts

@@ -3,6 +3,8 @@
 import {library} from '../models';
 import {context} from '../models';
 
+export function FullRescan():Promise<void>;
+
 export function GetAlbumTracks(arg1:number):Promise<Array<library.Track>>;
 
 export function GetAllAlbums():Promise<Array<library.Album>>;
@@ -12,3 +14,5 @@ export function GetAllTracks():Promise<Array<library.Track>>;
 export function Scan():Promise<void>;
 
 export function SetContext(arg1:context.Context):Promise<void>;
+
+export function SetQueue(arg1:library.queueClearer):Promise<void>;