Allow subfolders and new filenames for ss_new output

[k-doering-NOAA]

More details in #70 and #218.

Decide if it is appropriate (from internal team discussions and user feedback) to:

• Create subfolders for .ss_new and .sso output. E.g., could make it easier to delete output files.
• Split up data.ss_new into data_echo.ss_new, data_exp.ss_new, and dat_bootNNN.sss_new (or something similar. Based on comments from new_filename_and_folder_for_outputs #218 (comment) , this does seem like the SS3 team's preference, but names are subject to change.
• Consider renaming .ss_new files to just have the .ss extension. This could mean the files don't need to be renamed in order to be used.

[Rick-Methot-NOAA]

Clarification:
mcmc_output_detail is being used only to control the calling of bigreport from ss_proced:
//SS_Label_Info_7.12 #write report_mce_XXXX.sso and compreport_mce_XXXX.sso for each MCEVAL
if(mcmc_output_detail>=2) {
.......
write_bigreport();
}

Then in bigreport, the logic of creating separate filenames is controlled by
if(mceval_counter==0)
{write to report.sso}
else
{create new filename for each report}