feature: add dokuwiki functions to template parser

this commit adds an additional syntax to bureaucracy template parser that introduces simple functions calls:

    @function_name(arg)@

the functions are parsed after the fields replacements. this will work:

    @function(@@some_field@@)@

currently four functions are supported:
  - @curns()@
  - @getns()@
  - @nons()@
  - @p_get_first_heading()@

only functions with one argument are supported

i've found this useful when using bureaucracy together with struct's "Page" field. My use cases:

1. Use the page title in template replacement:

    @p_get_first_heading(@@schema.page@@)

2. In template action as new page name:
    action template tpl:template1 "somens:@nons(@@schema.page@@)@"

syntax.php

@@ -21,13 +21,15 @@ class syntax_plugin_bureaucracy extends DokuWiki_Syntax_Plugin {
     private $form_id = 0;
     var $patterns = array();
     var $values = array();
+    var $functions = array();
 
     /**
      * Prepare some replacements
      */
     public function __construct() {
         $this->prepareDateTimereplacements();
         $this->prepareNamespacetemplateReplacements();
+        $this->prepareFunctions();
     }
 
     /**
@@ -491,6 +493,17 @@ function replace($input, $strftime = true) {
             array($this, 'replacedate'),
             $input
         );
+
+        //run functions
+        foreach ($this->functions as $name => $callback) {
+            $pattern = '/@' . preg_quote($name) . '\((.*?)\)@/';
+            if (is_callable($callback)) {
+                $input = preg_replace_callback($pattern, function ($matches) use ($callback) {
+                    return call_user_func($callback, $matches[1]);
+                }, $input);
+            }
+        }
+
         return $input;
     }
 
@@ -543,8 +556,8 @@ function prepareNamespacetemplateReplacements() {
         $file = noNS($ID);
         $page = strtr($file, $conf['sepchar'], ' ');
         $this->values['__formpage_id__'] = $ID;
-        $this->values['__formpage_ns__'] = curNS($ID);
-        $this->values['__formpage_curns__'] = getNS($ID);
+        $this->values['__formpage_ns__'] = getNS($ID);
+        $this->values['__formpage_curns__'] = curNS($ID);
         $this->values['__formpage_file__'] = $file;
         $this->values['__formpage_!file__'] = utf8_ucfirst($file);
         $this->values['__formpage_!file!__'] = utf8_strtoupper($file);
@@ -576,4 +589,14 @@ function prepareDateTimereplacements() {
         $this->values['__timesec__'] = date('H:i:s');
 
     }
+
+    /**
+     * Functions that can be used after replacements
+     */
+    function prepareFunctions() {
+        $this->functions['curNS'] = 'curNS';
+        $this->functions['getNS'] = 'getNS';
+        $this->functions['noNS'] = 'noNS';
+        $this->functions['p_get_first_heading'] = 'p_get_first_heading';
+    }
 }