Added page content parsing to up-rank header text in search

This adds parsing of page content so that headers apply a boost to
scores in the search term index.
Additionally, this merges title and content terms to reduce the amount
of stored terms a little.
Includes testing to cover.

app/Entities/Models/Bookshelf.php

@@ -13,7 +13,7 @@ class Bookshelf extends Entity implements HasCoverImage
 
     protected $table = 'bookshelves';
 
-    public $searchFactor = 3;
+    public $searchFactor = 1.5;
 
     protected $fillable = ['name', 'description', 'image_id'];