UI: Always show menu on repo pages

Merges repo/sidebar.tmpl with repo/header.tmpl and makes every repo page use
middleware.RepoRef() necessary to display information on this menu.

templates/repo/wiki/new.tmpl

@@ -1,7 +1,6 @@
 {{template "base/head" .}}
 <div class="repository wiki new">
   {{template "repo/header" .}}
-  {{template "repo/sidebar" .}}
   <div class="ui container">
     {{template "base/alert" .}}
     <div class="ui header">

templates/repo/wiki/pages.tmpl

@@ -1,7 +1,6 @@
 {{template "base/head" .}}
 <div class="repository wiki pages">
 	{{template "repo/header" .}}
-	{{template "repo/sidebar" .}}
   <div class="ui container">
     <div class="ui header">
     	{{.i18n.Tr "repo.wiki.pages"}}

templates/repo/wiki/start.tmpl

@@ -1,7 +1,6 @@
 {{template "base/head" .}}
 <div class="repository wiki start">
 	{{template "repo/header" .}}
-	{{template "repo/sidebar" .}}
   <div class="ui container">
     <div class="ui center segment">
     	<span class="mega-octicon octicon-book"></span>

templates/repo/wiki/view.tmpl

@@ -1,7 +1,6 @@
 {{template "base/head" .}}
 <div class="repository wiki view">
 	{{template "repo/header" .}}
-	{{template "repo/sidebar" .}}
   <div class="ui container">
     <div class="ui grid">
       <div class="ui ten wide column">