Harmonize some options with their UI label

[acicovic]

Is your feature request related to a problem?

As time passes, our terminologies might change, and with it our settings page gets updates. Examples of this are "API Key" that has been renamed to "Site ID" and "Track as Page" that has been renamed to "Track as Non-Post".

In many of those cases, we quickly update the UI but not the underlying options. For example, the value of "Track as Non-Post" is still page. In large part, this is because renaming the options themselves can have undesired effects if not handled properly. However, this leads to out-of-sync code that can become harder to understand as time goes by.

Describe the solution you'd like

Find the affected options and give them a more representative name, making sure that:

• Nothing breaks.
• Upgrade path works.
• Downgrade path works.

Related PRs/issues:

• https://github.com/Parsely/wp-parsely/issues/799
• https://github.com/Parsely/wp-parsely/pull/1241

[GaryJones]

Renaming public methods and property names could be done on a major semantic versioning release.