[LorisInstance] add getModule function

LorisInstance already has functions to check if a module
exists, get the module directories, etc.

This adds a getModule to replace \Module::factory() so that
the code dealing with modules can be centralized in one place.

src/LorisInstance.php

@@ -76,7 +76,8 @@ public function getActiveModules(): array
         $modules = [];
         foreach ($mnames as $name) {
             try {
-                $modules[] = \Module::factory($this, $name);
+                $mod       = \Module::factory($this, $name);
+                $modules[] = $mod;
             } catch (\LorisModuleMissingException $e) {
                 error_log($e->getMessage() . " " . $e->getTraceAsString());
             }
@@ -116,6 +117,18 @@ public function hasModule(string $name) : bool
         return false;
     }
 
+    /**
+     * Get the \Module class for the module named $name,
+     * if enabled on this LORIS instance or throw an exception
+     * if it doesn't exist.
+     *
+     * @return \Module
+     */
+    public function getModule(string $name) : \Module
+    {
+        return \Module::factory($this, $name);
+    }
+
     /**
      * Returns an NDB_Config object used for interacting with configuration
      * settings for this instance.