Cache relations

[JN-Jones]

Laravel caches (as always) nothing, so the following code will run the same query three times:

$forum = Forum::find(1);

$forum->parent;
$forum->parent;
$forum->parent;

while the following code will do the same but run the query only once:

$forum = Forum::find(1);

Forum::find($forum->parent_id);
Forum::find($forum->parent_id);
Forum::find($forum->parent_id);

[wpillar]

Moving this to Beta 1 milestone, not essential for Alpha releases as it's an optimisation.