63: filter data, rearrange plugin includes

[benlk]

This PR is a WIP. 🚨

Changes

Housekeeping:

• rearranges plugin files so that each of the named classes has its own file, rather than having multiple classes per file: to help developers keep things straight

Implementation of #63 (comment) to allow filtering of options used by jquery.dfp.js:

• make a filter on $data before it's localised by calling apply_filters( 'dfw_js_data', $data ) on it
• figure out how to get jquery.dfw.js to load arbitrary options from the dfw option, same as the footer script.
  • What would probably work here is getting the keys on $data to be the appropriate keys for use as the configuration options that jQuery.dfp is looking for. But this might break other uses of network_code, and we should keep that in the dfw JSON object for legacy support.
• refactor DoubleClick::footer_script to draw from window.dfw instead of its own options

Why

For #63 and GDPR compliance

Testing/Questions

Questions that need to be answered before merging:

• does it work?

Steps to test this PR:

1. ...

[benlk]

This is probably not going to make it into 0.3 because of time constraints, but there's room for it in a follow-up release.

[benlk]

refactoring in progress, but the network code is not being output! dfpId is not being set to the value of the network_code option in window.dfp_options. In js/jquery.dfw.js, Object.assign should be returning the contents of dfw with the specified items overwriting the values in window.dfw.

[benlk]

Bumping to 0.4, sorry.

[benlk]

Testing complete locally; lazy-loaded and non- alike render.

Testing complete on a staging site using DFW to serve ads:

• ads still render
• UI has new labels