Shortcode container and sidebar registration hook

[miguelpeixe]

This PR improves the extensibility of the plugin:

• Ensure that inserted ads have a common <aside /> as container regardless of the action hook applied
• Allow a different plugin to disable the use of sidebars

If the scaip_shortcode_do_sidebar() can be removed to allow other hooks to be injected into scaip_shortcode, we should assume that a different placement logic is replacing the sidebar. The sidebar not being useful in this case, it should have the possibility to not be registered.

No changes should take place:

• Make sure ads are being placed with the proper <aside /> as its container
• Test the scaip_disable_sidebars filter by adding add_filter( 'scaip_disable_sidebars', '__return_true' ); in your theme functions.php file and confirming the sidebars are no longer registered on Appearance -> Widgets

[matticbot]

:tada: This PR is included in version 0.6.0-alpha.1 :tada:

The release is available on GitHub release

Your semantic-release bot :package::rocket:

[matticbot]

:tada: This PR is included in version 0.6.0 :tada:

The release is available on GitHub release

Your semantic-release bot :package::rocket: