forecast file option relF basis

[k-doering-NOAA]

https://github.com/nmfs-stock-synthesis/stock-synthesis/blob/55400063c66fa0742fdd797ab23040b1475ecb74/SS_benchfore.tpl#L374

Thanks @kellijohnson-NOAA for realizing the options 1 and 2 use a 1 or else{} statement. So it is possibly to incorrectly specify the rel F bias in the forecast input (e.g., as 0 or >2). Perhaps this should instead be a switch() statment with an error if the input is not valid.

[iantaylor-NOAA]

In some cases, the use of anything other than 1 as the alternative input might be fine, but in this case there's an error message which only works if a value of 2 is used as alternative to 1:
https://github.com/nmfs-stock-synthesis/stock-synthesis/blob/635c10f0b789d41538087b3533d9672a7df5cc75/SS_readdata_330.tpl#L3109

[Rick-Methot-NOAA]

Good to clean these up whever we find them. I agree that all should use explicit conditions, not relative conditions.

[Rick-Methot-NOAA]

fix by creating warning if read value is <1 or >2