add option to exclude STI subclasses from annotation

[ethnext]

I've added an option named exclude_sti_subclasses and code which checks if a model has a superclass under AR::B with the same table in order to exclude STI subclasses from annotation.

this is a need I have on a project with a large number of subclasses of certain models, where annotating every one generates a lot of noise on any schema change, so I prefer to just annotate the parent class.

[coveralls]

Coverage decreased (-51.8%) to 21.252% when pulling fea8f6a on venuenext:d_exclude_sti_subclasses into f1fa351 on ctran:develop.

[ecnalyr]

Is there a way to exclude a single file from the exclude_sti_subclasses option?

An opt-in option, opposite the opt-out option of # -*- SkipSchemaAnnotations.

[ethnext]

no, not as this is currently implemented

[coveralls]

Coverage decreased (-0.07%) to 72.994% when pulling 0416341 on venuenext:d_exclude_sti_subclasses into f1fa351 on ctran:develop.

[ecnalyr]

This doesn't look like it breaks anything: venuenext#1

[ctran]

Can you squash the commits and fix the broken CI tests? Thanks

[coveralls]

Coverage increased (+0.08%) to 73.588% when pulling ff76c18 on venuenext:d_exclude_sti_subclasses into 3b41216 on ctran:develop.

[coveralls]

Coverage increased (+0.08%) to 73.588% when pulling 694a44e on venuenext:d_exclude_sti_subclasses into 3b41216 on ctran:develop.

[ethnext]

not sure about the semaphore failure now. it doesn't look related to changes I made.

[ctran]

Thanks!