Feature / Add edit in customizer buttons

[stuartshields]

@westonruter and @valendesigns here is the initial concept for adding the Edit in Customizer button to the Posts/Pages edit screens. As well as adding Edit in Customizer to both post_row_actions and page_row_actions. I moved the customize url into it's own function since we're calling it in two different functions now.

[westonruter]

What about other plugins that add action links? I think an array_merge() is required.

[stuartshields]

@westonruter definitely.

[valendesigns]

Let's be consistent and use the same coding style. Other places in the plugin we would check if $post is an instance of WP_Post like this:

if ( ! ( $post instanceof WP_Post ) ) {
    return false;
}

[stuartshields]

@valendesigns Thanks I've now fixed it.

[valendesigns]

This one could also be updated.

[stuartshields]

@westonruter and @valendesigns This is ready for another look at. Any comments/direction would be good. As far as I can tell this is working the way we want it to, however I'm open to making this work better.

[valendesigns]

@stuartshields It appears you could just do away with the get_customize_url method altogether and use the static get_preview_post_link instead.

[stuartshields]

@valendesigns I wasn't able to get rid of get_customize_url altogether as it still needs the other variables that are generated to work. Latest commit has the fix, if you wanted to have a look.

[valendesigns]

@stuartshields The post object is all you need to generate the preview URL so you can totally replace the get_customize_url. What else do see as a requirement that get_preview_post_link doesn't offer?

[stuartshields]

@valendesigns I guess I'm concerned about not using get_customize_url because of #34 ... Do we continue with #34 but not use it for this one?

[valendesigns]

@stuartshields I've updated the PR a bit and resolved conflicts. All that's left is to add unit test coverage for the new methods.