Add a --skip-config flag to wp core multisite-convert (#231)

* Feat: provide support to skip config for multisite convert

Provided the support to skip the configuration of wp-config file by passing the --skip-config associate param. This is already being added for multiiste install command.

* Feat: Add functional tests for the --skip-config param to multisite-convert command

Author: hbhalodia

features/core.feature

@@ -381,3 +381,12 @@ Feature: Manage WordPress installation
       Warning: Multisite constants could not be written to 'wp-config.php'. You may need to add them manually:
       """
     And the return code should be 0
+
+  Scenario: Convert to WordPress multisite without adding multisite constants to wp-config file
+    Given a WP install
+
+    When I run `wp core multisite-convert --skip-config`
+    Then STDOUT should contain:
+    """
+    Addition of multisite constants to 'wp-config.php' skipped. You need to add them manually:
+    """

src/Core_Command.php

@@ -449,6 +449,9 @@ public function install( $args, $assoc_args ) {
 	 * [--subdomains]
 	 * : If passed, the network will use subdomains, instead of subdirectories. Doesn't work with 'localhost'.
 	 *
+	 * [--skip-config]
+	 * : Don't add multisite constants to wp-config.php.
+	 *
 	 * ## EXAMPLES
 	 *
 	 *     $ wp core multisite-convert