Fixed stairs & chests rendering

-Fixed chests rendering in inventory (kinda).
-Fixed stairs rendering.
From now on, all blocks with multiple states MUST have item model.
Example stair provided (though with incorrect textures).
Relates to #9.

src/main/resources/assets/appliedenergistics2/models/block/skystone.block.stairs.inner.json

@@ -0,0 +1,8 @@
+{
+  "parent": "block/inner_stairs",
+  "textures": {
+    "side": "appliedenergistics2:blocks/SkyStoneBlock.BLOCK",
+    "top": "appliedenergistics2:blocks/SkyStoneBlock.BLOCK",
+    "bottom": "appliedenergistics2:blocks/SkyStoneBlock.BLOCK"
+  }
+}

src/main/resources/assets/appliedenergistics2/models/block/skystone.block.stairs.json

@@ -0,0 +1,8 @@
+{
+  "parent": "block/stairs",
+  "textures": {
+    "side": "appliedenergistics2:blocks/SkyStoneBlock.BLOCK",
+    "top": "appliedenergistics2:blocks/SkyStoneBlock.BLOCK",
+    "bottom": "appliedenergistics2:blocks/SkyStoneBlock.BLOCK"
+  }
+}

src/main/resources/assets/appliedenergistics2/models/block/skystone.block.stairs.outer.json

@@ -0,0 +1,8 @@
+{
+  "parent": "block/outer_stairs",
+  "textures": {
+    "side": "appliedenergistics2:blocks/SkyStoneBlock.BLOCK",
+    "top": "appliedenergistics2:blocks/SkyStoneBlock.BLOCK",
+    "bottom": "appliedenergistics2:blocks/SkyStoneBlock.BLOCK"
+  }
+}