Allow user-defined filters for acoustic-trawl data inputs

[brandynlucca]

Support for enabling user-defined filters for age, length, transects, hauls, strata, etc., would be helpful for survey data where certain subsets of data are desired for one reason or another (e.g. age-1 dominated net hauls in 2015 from the FEAT hake survey). This relates to #239, which will be closed with this Issue once this feature/functionality is implemented.

• Is para.proc.age1_haul=[0] used in the parameter files? #239: user-argument for explicitly filtering out age-0 (or other age-classes)