320 standardize exit message

[nschindler-noaa]

What issue(s) does this PR address? Describe and add issue numbers, if applicable.

Link issue(s) here:

What tests have been done? Upload any model input files created for testing in a zip file, if possible.

What tests/review still need to be done? Who can do it, and by when is it needed (ideally)?

Check which is true. This PR requires:

• no further changes to r4ss
• no further changes to the manual
• no further changes to SSI (the SS3 GUI)
• no further changes to the stock synthesis change log (new features, bug reports)

Describe any changes in r4ss/SS3 manual/SSI/change log that are needed (if not checked):

Additional information (optional):

[nschindler-noaa]

This updates SS_readstarter.tpl to coding standards and implements write_warning for warning messages in SS_readstarter and SS_global.
example:
warnstream << "starter.ss has extra input lines; check echoinput to verify read"; // message to output
write_warning(N_warn,0,1); // N_warn (required), 0-whether to output to echoinput, 1-fatal flag (will output to cout and exit)

[Rick-Methot-NOAA]

Looks good Neal. Looking forward to using the new function throughout the code