Handling multiple lines with the single dish pipeline

[astrojysun]

The current single dish pipeline cannot handle data for multiple lines at the same time. After processing one line, the processing_singledish_{target} directory would contain all the done_step_X files, which cause the pipeline to skip all steps for all other lines.

It is possible to get around this in an ad-hoc way by processing one line at a time and renaming that processing_singledish_{target} directory to something else each time. A more permanent solution would involve modifying the pipeline so that the generated done_step_X files are named like done_step_X_{line} (and same for all other files).