builder.isSingleFile should be a bool, not an int.

git-svn-id: svn://svn.transmissionbt.com/Transmission/trunk@14287 f4695dd4-2c0a-0410-b89c-da849a56a58e
separate out the sandbox code so that test sandboxes can be created without a tr_session

git-svn-id: svn://svn.transmissionbt.com/Transmission/trunk@14288 f4695dd4-2c0a-0410-b89c-da849a56a58e