Move common image files to pcl/io/ during the installation; fix block alignments.

This is related to issue https://github.com/kwaegel/pcl/issues/6 and some comments you got on https://github.com/PointCloudLibrary/pcl/pull/276. It installs common image* files in pcl/io.

Also fixed alignment of blocks inside CMakeLists.txt and replaced TAB characters by spaces.