Refactor config package

- Parse configuration only once during startup time
- Store configuration values in a global variable

ui/handler.go

@@ -2,10 +2,9 @@
 // Use of this source code is governed by the Apache 2.0
 // license that can be found in the LICENSE file.
 
-package ui  // import "miniflux.app/ui"
+package ui // import "miniflux.app/ui"
 
 import (
-	"miniflux.app/config"
 	"miniflux.app/reader/feed"
 	"miniflux.app/storage"
 	"miniflux.app/template"
@@ -16,7 +15,6 @@ import (
 
 type handler struct {
 	router      *mux.Router
-	cfg         *config.Config
 	store       *storage.Storage
 	tpl         *template.Engine
 	pool        *worker.Pool