add 'reader' group

it is essentially the same as 'anon' but 'reader' is allowed to log in
if wiki is locked down.

admin/view_edit_user.html

@@ -20,6 +20,7 @@
 			<div class="form-field">
 				<select id="group" name="group" aria-label="{{block "group" .}}Group{{end}}">
 					<option {{if .Form.Get "group" | eq "anon" }}selected{{end}}>anon</option>
+					<option {{if .Form.Get "group" | eq "reader" }}selected{{end}}>reader</option>
 					<option {{if .Form.Get "group" | eq "editor" }}selected{{end}}>editor</option>
 					<option {{if .Form.Get "group" | eq "trusted" }}selected{{end}}>trusted</option>
 					<option {{if .Form.Get "group" | eq "moderator" }}selected{{end}}>moderator</option>
@@ -36,4 +37,4 @@
 		<p>{{block "delete user tip" .}}Remove the user from the database. Changes made by the user will be preserved. It will be possible to take this username later.{{end}}</p>
 		<a class="btn btn_destructive" href="/admin/users/{{.U.Name}}/delete">{{template "delete"}}</a>
 	</main>
-{{end}}
+{{end}}

admin/view_new_user.html

@@ -25,6 +25,7 @@
 				<label for="group">{{block "group" .}}Group{{end}}:</label>
 				<select id="group" name="group">
 					<option {{if .Form.Get "group" | eq "anon" }}selected{{end}}>anon</option>
+					<option {{if .Form.Get "group" | eq "reader" }}selected{{end}}>reader</option>
 					<option {{if .Form.Get "group" | eq "editor" }}selected{{end}}>editor</option>
 					<option {{if .Form.Get "group" | eq "trusted" }}selected{{end}}>trusted</option>
 					<option {{if .Form.Get "group" | eq "moderator" }}selected{{end}}>moderator</option>
@@ -40,4 +41,4 @@
 			</div>
 		</form>
 	</main>
-{{end}}
+{{end}}

user/user.go

@@ -48,6 +48,7 @@ var minimalRights = map[string]int{
 
 var groups = []string{
 	"anon",
+	"reader",
 	"editor",
 	"trusted",
 	"moderator",
@@ -57,6 +58,7 @@ var groups = []string{
 // Group — Right level
 var groupRight = map[string]int{
 	"anon":      0,
+	"reader":    0,
 	"editor":    1,
 	"trusted":   2,
 	"moderator": 3,