make avatar lookup occur at image request (#10540)

speed up page generation by making avatar lookup occur at the browser
not at page generation

* Protect against evil email address ".."

* hash the complete email address

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-Authored-By: Lauris BH <lauris@nix.lv>

modules/templates/helper.go

@@ -85,7 +85,7 @@ func NewFuncMap() []template.FuncMap {
 		"AllowedReactions": func() []string {
 			return setting.UI.Reactions
 		},
-		"AvatarLink":    base.AvatarLink,
+		"AvatarLink":    models.AvatarLink,
 		"Safe":          Safe,
 		"SafeJS":        SafeJS,
 		"Str2html":      Str2html,