Admin notice add user friendly Error message for non Dual CC-Woo Install

[bahiirwa]

I think we need to add an admin notice to make this Error message for meaningful for the ordinary user who might have skipped the documentation and also reduce the support call.

Suggestion:

1. User clicks to install CC.
2. Stop CC install to Detect the WooCommerce ( Need to find a unique function to Woo not in CC ).
3. Throw the notice to deactivate Woo.
4. Notice provides: A link to the plugins deactivation for woo.
5. User can now activate CC.

I know Woocommerce won't be supporting any forks after < WP 5.0. However someone might migrate with an older version of Woo. We have to have this in mind as we move with this ticket.

Originally posted by @bahiirwa in #136 (comment)

[nylen]

2. Stop CC install to Detect the WooCommerce ( Need to find a unique function to Woo not in CC ).

Probably a better way to handle this is to stop Classic Commerce from loading just before the declaration of the function wc() in Classic Commerce, something like this:

function cc_wc_already_active_notice() {
    echo '<div class="error"><p>';
    echo __( 'You must deactivate WooCommerce before activating Classic Commerce.', 'classic-commerce' );
    echo '</p></div>';
}
if ( function_exists( 'wc' ) ) {
    // The main wc() function already exists, which means WooCommerce is active.
    // Show an admin notice.
    add_action( 'admin_notices', 'cc_wc_already_active_notice' );
    // Deactivate Classic Commerce.
    deactivate_plugins( array( 'classic-commerce/classic-commerce.php' ) );
    // Do not proceed further with Classic Commerce loading.
    // (may need tweaking depending on code structure)
    return;
}

function wc() {
    // ... (existing code)

[timbocode]

This looks good to me.

[nylen]

Looks like this was closed by mistake? The PR #154 does something else.

[bahiirwa]

Good catch.