IFF: add support for RGBN/RGB8 image data and CAT chunk

Add the following features:
- RGB8 image data support (test case added)
- RGBN image data support ([Clouds.iff](/uploads/9db869350f74421bf1813fa7d4332f4f/Clouds.iff))
- CAT chunk support: you can have more than one image for file (test case added)
- Image transformation support via EXIF data

[RGBN/RGB8](https://wiki.amigaos.net/wiki/RGBN_and_RGB8_IFF_Image_Data) files are used in Impulse's Turbo Silver and Imagine.

Closes #34

autotests/read/iff/cat_ilbm.iff.json

@@ -0,0 +1,5 @@
+[
+    {
+        "fileName" : "ps_testcard_rgb_maya.png"
+    }
+]

autotests/read/iff/sv5_testcard_rgb_rgb8.iff.json

@@ -0,0 +1,5 @@
+[
+    {
+        "fileName" : "ps_testcard_rgb_maya.png"
+    }
+]