Master

• The customXform property no longer exists. Instead, NiftiOpts.transform can take a value of reference, in which case the voxel->display transform is calculated from the current DisplayContext.displaySpace
• Texture3D now only allows 1-channel and 3-channel textures. It also uses GL_RED if possible for 1-channel textures, because using GL_LUMINANCE caused problems on some platforms (issue #70 (closed))
• Fixed issue in test_in_bounds.glsl - some GLSL compilers error on double-undesccores
• Edit transform panel now shows a warning if display space is not suitable, instead of changing the display space
• Fixed bug in screenshot action - was always saving to cwd
• Fixed some issues in parseargs