add csv and xlsx formats

[ETLaurent]

Summary

Untie gzip method to build something more agnostic in order to be able to add other formats (such as formats which do not have multiple compressed files, but just a simple export file, like a CSV file for instance).

Add CSV format.
XLSX is added via a separate module: https://github.com/apostrophecms/import-export-xlsx (see PR).

Non-exhaustive list of the work done to separate concerns:

• no apos instance in format files
• no format specific stuff inside import.js and export.js files
• usage of callbacks to deal with apos-specific attachment business in the gzip format and format-specific files handling on apostrophe side (ie: concerns are separated)
• gzip import function handles the extraction AND the deletion of the archive on its own

Other improvements:

• better handling of the streams and their error events
• better handling and clarification of the double format.input() call, whether it is called with overrideLocale: true or not
• refactor remove functions into one (except in gzip format where the remove function is standalone)
• add logs:
  • on import and export side (prefixed by [import] and [export])
  • on formats side ([csv], [gzip], [xlsx])
• add documentation to explain how add and register new formats

What are the specific steps to test this change?

For example:

1. Run the website and log in as an admin
2. Open a piece manager modal and select several pieces
3. Click the "Archive" button on the top left of the manager and confirm that it should proceed
4. Check that all pieces have been archived properly

What kind of change does this PR introduce?

(Check at least one)

• Bug fix
• New feature
• Refactor
• Documentation
• Build-related changes
• Other

Make sure the PR fulfills these requirements:

• It includes a) the existing issue ID being resolved, b) a convincing reason for adding this feature, or c) a clear description of the bug it resolves
• The changelog is updated
• Related documentation has been updated
• Related tests have been updated

If adding a new feature without an already open issue, it's best to open a feature request issue first and wait for approval before working on it.

Other information:

[linear]

PRO-5809 Handle dependency on a vulnerable version of Excel by deprecating the import-export module and importer module.

[ETLaurent]

moved to import.js

[ETLaurent]

moved from export.js

[ETLaurent]

tests run in https://github.com/apostrophecms/testbed/pull/242