320 standardize exit message

[nschindler-noaa]

Concisely (20 words or less) describe the issue

converted SS_readdata_330.tpl to use write_warning for warn messages.

Please Link issue(s)

issue #320

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

compiles, ran Big_Skate_2019 with no problems

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

Has any new code been documented?

write_warning is in SS_global.tpl
code in SS_readdata_330 has been changed and reduced a little.

If not, please add documentation before submitting the Pull Request.

• I have documented any new code added (or no new code was added)

is there an input change for users to Stock Synthesis?

No input changes

• Yes, there was an input change

If so, please provide an example of the new inputs needed.

[New example stock synthesis input goes here]

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 that are needed (if not checked):

If changes are needed in the change log, please fill in the table here:

Action	Topics	Type
[fix, new, or revise]	[e.g., biology. Use issue label options.]	[input, output, and/or calc, or ALL]

Additional information (optional):

[Rick-Methot-NOAA]

thanks Neal

[nschindler-noaa]

Rick, this is ready for merge.

[nschindler-noaa]

Next up: SS_readcontrol_330.tpl