Correcting reported Doxygen syntax warnings.

Fixed wrong Doxygen syntax and add some of the available FIXME to
Doxygen documentation.
Updated Doxygen configuration to add also all capital letter tags.
Adding some more Doxygen documentation.

include/ITemplateEngine.php

@@ -1,11 +1,10 @@
-<?php
-require_once 'boot.php';
-
-
-/**
- * Interface for template engines
- */
-interface ITemplateEngine {
-	public function replace_macros($s,$v);
-	public function get_markup_template($file, $root='');
-}
+<?php
+require_once 'boot.php';
+
+/**
+ * @brief Interface for template engines.
+ */
+interface ITemplateEngine {
+	public function replace_macros($s, $v);
+	public function get_markup_template($file, $root='');
+}