Add option to configure allowed '--fix' parameters / allowed 'write_list' entries

[frq-asgard-josi]

Use case

We would like to configure a subset of autofixes in the .ansible-lint config file which are applied when using the --fix option. We do however, not want to enable --fix by default. Users should still be able to use ansible-lint without having their files changed.
Currently the only way to exclude autofixes is by specifying the write_list in the config file but this automatically applies --fix even if ommited in the command.

Proposed Solution

To solve this, we could use an additional 'write_exclude_list' parameter to specify which autofixes we want to disable. This should be completely backwards compatible since we wouldn't change the behavior of existing config options in any way.

[frq-asgard-josi]

For internal use we already added a patch providing this functionality. I could provide this as a PR if this proposal receives positive feedback.