Consistently name properties and keep structure as flat as possible

[wpscholar]

This is the current state of our prepareRuntime() method: https://github.com/newfold-labs/wp-module-runtime/blob/trunk/includes/Runtime.php#L39-L52

There are a few things missing:

• restUrl
• restNonce

Given that all these properties are going to be used in JavaScript, we should use camel-case as the naming convention:

• Rename admin_url to adminUrl (we can keep the old for backward compatibility until references are all removed)
• Rename base_url to homeUrl (this is what it is actually referencing, but we shouldn't append the index.php part)
• Rename site.url to siteUrl

We should also strive to flatten the structure where possible. For example, we should remove the sdk property and just let its contents live at the top level. Additionally, site.title should just become siteTitle.

It is okay to nest things, but only where it makes logical sense and doesn't over-complicate data fetching. For example, having a capabilities property that contains an object of capability mappings is fine.

[aulisius]

Closed by #7