Move LDAP libs to optional 'suggest' block in order to not block installation when php-ldap extension is missing

composer.json-dist

@@ -41,13 +41,15 @@
         "pear-pear.php.net/auth_sasl": ">=1.0.6",
         "pear-pear.php.net/net_idna2": ">=0.1.1",
         "pear-pear.php.net/net_sieve": ">=1.3.2",
-        "pear-pear.php.net/net_ldap2": ">=2.0.12",
-        "kolab/Net_LDAP3": "dev-master",
         "patchwork/utf8": "1.2.x"
     },
     "require-dev": {
         "pear-pear.php.net/crypt_gpg": "*",
         "phpunit/phpunit": "*"
     },
+    "suggest": {
+        "pear-pear.php.net/net_ldap2": "Version >=2.0.12 required for connecting to LDAP address books",
+        "kolab/Net_LDAP3": "dev-master required for connecting to LDAP address books"
+    },
     "minimum-stability": "dev"
 }