Annotate pylintrc w defaults and rationale

Generated from 'pylint --generate-rcfile'.

Defaults are commented out.

Exceptions to defaults include a rationale.

Note generation of 'pylintrc_reduced'.

Minor changes to code to conform w/ new config.
Right.  I tested removing each of them (the ones remaining, too), in order to figure out the `RATIONALE:` bits, and removed those which either triggered no errors or which could be handled otherwise.  I also tweaked code in a couple of places to make the 'disable' unnecessary (the format attributes and the `_get_protobuf_attribute_and_value` rename).