feat: allow disable directives within the XML configuration

[DinoChiesa]

This addresses #444 .

It allows suppressing errors or warnings, generated on a particular file, with the inclusion of a comment in the specific XML file. The comment should look like this:

  <!-- apigeelint disable=TD004 -->

It needs to appear on the line before the line that would be mentioned in the error or warning.

Also:

• updated TD002 to use the correct line number in the warnings, so that they can be properly disabled.
• updated BN012 to use the correct module in the error message.
• updated BN012 test to be more robust.
• added a command-line switch to disable this feature.
• added tests for this feature as well as the command-line switch.
• updated README describing this feature.

[DinoChiesa]

Reviewers: see if you think the name of the command-line switch is a good one. Or, if you have a suggestion for a better option, please offer it!

[DinoChiesa]

Please review again?

[ssvaidyanathan]

LGTM