Fix indentation. Update doxygen comments

include/sta/mutex.hpp

@@ -8,23 +8,25 @@
 
 namespace sta
 {
-	/**
-	 * @brief Interface for mutex objects.
-	 */
-	class Mutex
-	{
-	public:
-		/**
-		 * @brief Block until mutex has been acquired.
-		 */
-		virtual void acquire() = 0;
-		/**
-		 * @brief Release mutex.
-		 */
-		virtual void release() = 0;
+    /**
+     * @brief Interface for mutex objects.
+     *
+     * @ingroup sta_core
+     */
+    class Mutex
+    {
+    public:
+        /**
+         * @brief Block until mutex has been acquired.
+         */
+        virtual void acquire() = 0;
+        /**
+         * @brief Release mutex.
+         */
+        virtual void release() = 0;
 
-		static Mutex * ALWAYS_FREE; /**< Fake mutex that can always be acquired */
-	};
+        static Mutex * ALWAYS_FREE; /**< Fake mutex that can always be acquired */
+    };
 } // namespace sta