when a project is passed on the command line on appleseed.studio, don't print the same error message twice if the project could not be loaded.
Merge pull request #248 from est77/blender_appleseed_addon

Blender appleseed addon work
in appleseed.studio, replaced the --final-render command line option by a --render option that takes the name of a render configuration in argument.  rendering no longer starts if no --render option is present.
Merge branch 'master' of github.com:jupiter-jazz/appleseed
updated and cleaned up the Python sample, added data directory.
formatting fixes.
updated copyright notice.
Minor blender addon work.
Merge branch 'master' into blender_appleseed_addon