Multiple changes

There are now five bushes in this mod: strawberry, blackberry,
blueberry, raspberry, and gooseberry.

Instead of giving you the fruit, digging a bush now directly gives you
that bush, with a 1/5 chance of getting two.

Craft one bush by itself to turn it into four of the corresponding
fruit.  Craft six of that fruit to get the bush back (this is how it was
before, I opted to keep it that way).

Craft:

- - -
S J S
f f f

That is, two sugar, one jungle grass, and three fruit as before, to get
one raw pie of that fruit.  Cook it as usual.  Heals 2 hearts.

Craft one whole pie by itself to get four slices, each of which heals
1/2 heart.

Craft:

S J S
f f f
f f f

That is, two sugar, one jungle grass, and mix-and-match six fruits to
get two mixed fruit pies.  Cook as usual, craft one to get four slices.

Baskets of pies can be crafted the same as before (craft a basket from
four sticks in a "T" shape, then craft one of those plus three pies of
the desired type).

In addition: some moderate rewriting and re-arranging of the code to
facilitating adding the new objects.

Made the bushes lower-resolution (they were 64px, which made them not
fit in so well into the usual 16px landscape - reduced them to 32px.
Ditto for the basket textures.  Pies are all 16px.

New textures for the pies.