Add JPEG 2000 support

JPEG 2000 support using OpenJPEG library.

- Add read/write support to JP2/J2K format for Gray/RGB(A)/CMYK images @8/16-bits
- Read test case images generated by Photoshop

The plugin has the following limitations:
- Resolution is not set (JP2_RES box is marked "For the future" in jp2.h)
- Metadata are not set (as with resolution)

Closes #13

autotests/read/jp2/testcard_cmyk.jp2.json

@@ -0,0 +1,11 @@
+[
+    {
+        "minQtVersion" : "6.8.0",
+        "fileName" : "testcard_cmyk.tif"
+    },
+    {
+        "maxQtVersion" : "6.7.99",
+        "unsupportedFormat" : true,
+        "comment" : "Qt versions lower than 6.8 do not support CMYK format so this test should be skipped."
+    }
+]