Move the code documenting chapter up and put PHPDoc in a sub-section

There are other documentation tools out there. At the least there should be the possibility to add these.

_posts/15-01-01-Documenting.md

@@ -0,0 +1,5 @@
+---
+anchor: documenting
+---
+
+# Documenting your Code {#documenting_title}

_posts/15-02-01-PHPDoc.md

@@ -1,8 +1,10 @@
 ---
-anchor: phpdoc
+isChild: true
+title:   PHPDoc
+anchor:  phpdoc
 ---
 
-# PHPDoc {#phpdoc}
+## PHPDoc {#phpdoc_title}
 
 PHPDoc is an informal standard for commenting PHP code. There are a *lot* of different [tags] available. The full list
 of tags and examples can be found at the [PHPDoc manual].