Add UI for viewing the album info returned by Subsonic getAlbumInfo API

- Adding "Get Info" in album page's "meatball" menu. When the option is clicked a pop up appears with
the album information and links to Last.fm and MusicBrainz.

Screenshot:

Fixes #105

ui/browsing/albumpage.go

@@ -203,7 +203,9 @@ func NewAlbumPageHeader(page *AlbumPage) *AlbumPageHeader {
 				}),
 				fyne.NewMenuItem("Download...", func() {
 					a.page.contr.ShowDownloadDialog(a.page.tracks, a.titleLabel.String())
-			
+				}),
+				fyne.NewMenuItem("Get Info...", func() {
+					a.page.contr.ShowAlbumInfoDialog(a.albumID, a.titleLabel.String(), a.cover.Image.Image)
 				}))
 			pop = widget.NewPopUpMenu(menu, fyne.CurrentApp().Driver().CanvasForObject(a))
 		}