Added CallbackApp to better access backend.Backend from with in an App

Fixed issues with CORS not being able to do an OPTIONS request
Fixed folders not being processed properly.
Fixed some other issues.

internal/blog/main.go

@@ -16,9 +16,8 @@ type BlogApp struct {
 	conv         *bbConvert.HTMLConverter
 }
 
-func NewBlogApp(b *backend.Backend, db *mongo.Database) *BlogApp {
+func NewBlogApp(db *mongo.Database) *BlogApp {
 	out := &BlogApp{
-		back:         b,
 		blogCol:      db.Collection("blog"),
 		authCol:      db.Collection("author"),
 		portfolioCol: db.Collection("portfolio"),
@@ -40,6 +39,10 @@ func (b *BlogApp) CrashTable() backend.CrashTable {
 	return nil
 }
 
+func (b *BlogApp) AddBackend(back *backend.Backend) {
+	b.back = back
+}
+
 func (b *BlogApp) Extension(mux *http.ServeMux) {
 	mux.HandleFunc("GET /blog", b.reqLatestBlogs)
 	mux.HandleFunc("GET /blog/list", b.reqBlogList)