Ability to generate only model

[kobylynskyi]

Is your feature request related to a problem? Please describe.
Sometimes developers need to generate only model classes (types/enums/inputs/etc.)

Describe the solution you'd like
Extend MappingConfig with 2 new attributes:

• generateApis - true by default
• generateModels - true by default

[PavelSusloparov]

That's totally my use case, need to generate model only.

[kobylynskyi]

Done in 1.2