document why pylint has a large set of messages disabled by default

[fermulator]

Steps to reproduce

1. run : "python -m pylint --generate-rcfile | grep disable="

Current behavior

The default value for pylint is populated with a generous number of messages into the "disable" configuration by default.

This list is documented : https://pylint.readthedocs.io/en/latest/reference_guide/features.html#messages-control-options

Expected behavior

We should document WHY this list is here.

This will help users decide if they should keep that default list, or wipe it and start fresh with their own customized list.

pylint --version output

$ python35 -m pylint --version
No config file found, using default configuration
main.py 1.5.5,
astroid 1.4.5
Python 3.5.1 (default, Dec 11 2015, 13:17:22)
[GCC 4.8.3 20140911 (Red Hat 4.8.3-9)]