Disable all rules or a list of specific rules in the entire file (#1029)

[paul-dingemans]

Description

Add support to disable all rules in the entire file with:

@file:Suppress("ktlint")

or with a named list of rules:

@file:Suppress("ktlint:no-foo-identifier-standard", "ktlint:custom:no-foo-identifier")

Closes #1029

Checklist

• PR description added
• tests are added
• CHANGELOG.md is updated

In case of adding a new rule:

• README.md is updated
• Rule has been applied on Ktlint itself and violations are fixed