[LINST] Add .meta option to skip XIN rules (aces#8714)

XIN rules default to requiring everything unless otherwise
specified. This is not useful for all instruments (for instance,
LINST files that are used to import data from other systems where
we don't support their rule format) so this adds an option
to disable the rules for an instrument in the .meta file.

php/libraries/NDB_BVL_Instrument_LINST.class.inc

@@ -44,6 +44,11 @@ class NDB_BVL_Instrument_LINST extends \NDB_BVL_Instrument
     // array of the format "field_name" => "group_name"
     protected $GroupElements = [];
 
+    /**
+     * Do not require rules by default.
+     */
+    private $skipRules = false;
+
     /**
      * Sets up the variables required for a LINST instrument to load
      *
@@ -413,7 +418,9 @@ class NDB_BVL_Instrument_LINST extends \NDB_BVL_Instrument
             }
             $this->formType = 'XIN';
 
-            $this->form->addFormRule([&$this, 'XINValidate']);
+            if (!$this->skipRules) {
+                $this->form->addFormRule([&$this, 'XINValidate']);
+            }
             $fp = fopen($filename, "r");
 
             // Add elements is only true if we're parsing the current page,
@@ -927,6 +934,9 @@ class NDB_BVL_Instrument_LINST extends \NDB_BVL_Instrument
             case 'postmortem':
                 $this->postMortem = trim($pieces[1]) === 'true';
                 break;
+            case 'norules':
+                $this->skipRules = trim($pieces[1]) === 'true';
+                break;
             default:
                 break;
             }