new CLI command: Enable Template Hints

[miguelbalparda]

In order to help developers to work with the Magento CLI, create new commands which will simplify the debugging of the application. Currently, enabling of these setting require doing that either with the UI or changing the configuration of the di.xml.

Description

Added a CLI switch to enable/disable template hints.

Fixed Issues (if relevant)

1. Create new CLI command: Enable Template Hints #9278 Create new CLI command: Enable Template Hints

Manual testing scenarios

1. php bin/magento dev:template-hints:enable
2. Check for dev/debug/template_hints_storefront to be 1
3. php bin/magento dev:template-hints:disable
4. Check for dev/debug/template_hints_storefront to be 0

*. A cache flush is required both from the CLI and from the web UI after template paths are enabled/disabled in order for the hints to show. This should probably be in the success message, not really sure how to word it.

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

Submitted at #mm17se contribution day

[miguelbalparda]

@okorshenko this is ready from my side, I'll try to keep working on this later to add an extra parameter for the scope but for now this is it.

[magento-team]

@miguelbalparda thank you for your contribution