Make custom items work as ingredients in custom recipes, also small tag-fix to <l@location.inventory>

In my very first contribution to denizen i want to add a solution for making custom items from itemscripts work as ingredients for other itemscript recipes.
I therefore made the dMaterial.matches function more strict to only accept valid materials, and I used it to check recipe contents.

Recipes like

    - i@Brownstick|i@Dice|air
    - white_wool|stick|white_wool
    - i@Beerbotle|stone|i@Yellowstick

are possible now.

I also saw a small typo in the &lt;l@location.inventory&gt; tag after I saw issue 523, should be fixed now.