Flatten structure of test/extension/io/output/ folder (#400)

There is no need for format-specific subfolders.
There is no code in place that checks if all those folders exist and
creates them.
This change simplifies the structure to simplify running of I/O tests.

Rename images/jpg/ to images/jpeg/ in tests
The `jpeg` is name of the format used in the I/O extension and
the folders inside `images/` are named after those formats.

test/extension/io/.gitignore

@@ -1 +1,9 @@
-/output/
+/output/*.bmp
+/output/*.crw
+/output/*.jpg
+/output/*.jpeg
+/output/*.png
+/output/*.pnm
+/output/*.tga
+/output/*.tif
+/output/*.tiff

test/extension/io/paths.hpp

@@ -34,25 +34,25 @@
 static const std::string base = (boost::filesystem::absolute(boost::filesystem::path(__FILE__)).parent_path().string()) + "/";
 
 static const std::string bmp_in  = base + "images/bmp/";
-static const std::string bmp_out = base + "output/bmp/";
+static const std::string bmp_out = base + "output/";
 
-static const std::string jpeg_in  = base + "images/jpg/";
-static const std::string jpeg_out = base + "output/jpeg/";
+static const std::string jpeg_in  = base + "images/jpeg/";
+static const std::string jpeg_out = base + "output/";
 
 static const std::string png_base_in = base + "images/png/";
 static const std::string png_in      = png_base_in + "PngSuite/";
-static const std::string png_out     = base + "output/png/";
+static const std::string png_out     = base + "output/";
 
 static const std::string pnm_in  = base + "images/pnm/";
-static const std::string pnm_out = base + "output/pnm/";
+static const std::string pnm_out = base + "output/";
 
 static const std::string raw_in  = base + "images/raw/";
 
 static const std::string targa_in  = base + "images/targa/";
-static const std::string targa_out = base + "output/targa/";
+static const std::string targa_out = base + "output/";
 
 static const std::string tiff_in    = base + "images/tiff/";
-static const std::string tiff_out   = base + "output/tiff/";
+static const std::string tiff_out   = base + "output/";
 static const std::string tiff_in_GM = tiff_in + "graphicmagick/";
 
 static const std::string bmp_filename  ( bmp_in      + "test.bmp"               );