make models (plural) instead of make model

[cneud]

Multiple models are indeed used plus this makes naming consistent with other Makefiles.

[mikegerber]

I had a look on other Makefiles to check for consistency:

• ocrd_calamari: Uses a different target name
• ocrd_tesserocr: Does not have a model download in the Makefile
• sbb_textline_detection: Does not have a model download in the Makefile
• ocrd_cis: Does not have a model download in the Makefile

So I guess it's up to us how to name this. (There is resource management coming in OCR-D/core#559 but that only pertains to OCR-D.)

[mikegerber]

LGTM

[cneud]

I think I checked eynollah for a reference Makefile convention to use.

Moreover, the current version of sbb_binarization does indeed leverage multiple models - btw this it seems is also not properly exposed here.

Anyway I understand that meanwhile @vahidrezanezhad has trained a newer and uniform model so that future versions will only require a single model file...