Add basic title edition

Fix #218
I mean basic, because there is no javascript at all. It could be a nice edit-in-place. But for the moment, it is simple.

src/Wallabag/CoreBundle/Entity/Entry.php

@@ -390,7 +390,7 @@ class Entry
     /**
      * @param bool $isPublic
      */
-    public function setPublic($isPublic)
+    public function setIsPublic($isPublic)
     {
         $this->isPublic = $isPublic;
     }

src/Wallabag/CoreBundle/Entity/Tag.php

@@ -51,6 +51,12 @@ class Tag
         $this->user    = $user;
         $this->entries = new ArrayCollection();
     }
+
+    public function __toString()
+    {
+        return $this->label;
+    }
+
     /**
      * Get id.
      *