Add D-M-test.zip to test models

[e-perl-NOAA]

@Rick-Methot-NOAA suggested adding the
D-M_test.zip to the test model files in ss3-source-code PR #542.

@Rick-Methot-NOAA can you tell me more about this model?

[e-perl-NOAA]

Simple_with_DM_sizefreq - Simple model with generalized size composition data with D-M

[Rick-Methot-NOAA]

This model is a derivative of simple.

• two areas with identical fisheries and surveys in both areas
• two seasons of unequal durations with all catch in season 1
• adds fleet 7 as a depletion survey
• adds generalized size comp data in same units as the length comp data (2 cm bins). Data are identical to the length comp data, so logL should be the same.
• adds D-M for fleets 1, 2, 3, 4 and all use the same shared parameter.
• note that fleet 3 has no comp data so D-M is irrelevant; note that fleet 5 has comp data but does not have D-M so provides a comparison to fleet 2.