Restrict permission check on repositories and fix some problems (#5314)

* fix units permission problems

* fix some bugs and merge LoadUnits to repoAssignment

* refactor permission struct and add some copyright heads

* remove unused codes

* fix routes units check

* improve permission check

* add unit tests for permission

* fix typo

* fix tests

* fix some routes

* fix api permission check

* improve permission check

* fix some permission check

* fix tests

* fix tests

* improve some permission check

* fix some permission check

* refactor AccessLevel

* fix bug

* fix tests

* fix tests

* fix tests

* fix AccessLevel

* rename CanAccess

* fix tests

* fix comment

* fix bug

* add missing unit for test repos

* fix bug

* rename some functions

* fix routes check

templates/repo/home.tmpl

@@ -25,9 +25,9 @@
 		</div>
 		<div class="ui repo-topic" id="repo-topic">
 		{{range .Topics}}<a class="ui green basic label topic" style="cursor:pointer;" href="{{AppSubUrl}}/explore/repos?q={{.Name}}&topic=1">{{.Name}}</a>{{end}}
-		{{if .IsRepositoryAdmin}}<a id="manage_topic" style="cursor:pointer;margin-left:10px;">{{.i18n.Tr "repo.topic.manage_topics"}}</a>{{end}}
+		{{if .Permission.IsAdmin}}<a id="manage_topic" style="cursor:pointer;margin-left:10px;">{{.i18n.Tr "repo.topic.manage_topics"}}</a>{{end}}
 		</div>
-		{{if .IsRepositoryAdmin}}
+		{{if .Permission.IsAdmin}}
 		<div class="ui repo-topic-edit grid form segment error" id="topic_edit" style="display:none">
 			<div class="fourteen wide column">
 				<div class="field">