Output file names or directories should reflect scenario name

[mfripp]

Various functions now produce standardized output files. However, when multiple scenarios are run in the same directory, the later output files usually overwrite the earlier ones, making them irretrievable.

We should modify these output functions, so that if a scenario name is defined in model.options.scenario_name, it will be appended to the file name or used to define a subdirectory within outputs/, where all the output files will be stored. Either of these would make it possible to save results from multiple scenarios and then retrieve them later.

The reporting routines in the switch.hawaii modules append the scenario name to the end of each file. This makes it easy to browse for a particular output file, e.g., to open it in Excel. The subdirectory option would be neater, but would also take a little more digging to inspect the results.