Plan for Nodewords v6.x-3.0 release

Nodewords 3.0 will be the last major release. There are a few key issues that need to be dealt with, specific feature additions that have long been needed.

Tentative plan:

• #945676: Allow defaults to be defined per content type
• #1269728: META: Plan for Metatag 7.x-1.0 release - Nodewords v3 will happen after Metatag 1.0.
• #1380362: Re-implement Token integration
• #1664324: Add support for Twitter's new "cards" metatags
• #2100615: Group meta tags by their type, e.g. basic, advanced, DC, OG
• #2274041: Add entire issue queue into Trello - so we can fully understand what the current problems are with the module.
• .. and deal with the necessary API changes.
• Closer feature parity with Metatag, primarily the meta tags supported and their default values.

The plan is also being organized via a Trello board: https://trello.com/b/GTRdtWe1/nodewords

FYI we'll be jumping to v3 in an effort to distance it from the ill-fated v2 that was abandoned.