Work towards #56: Splitting up the README

I did the job and splitted up the readme, hopefully everything was
splitted correctly...

dao/index.md

@@ -0,0 +1,17 @@
+---
+layout: pattern
+title: Data Access Object
+folder: dao
+categories: pattern_cat
+tags: pattern_tag
+---
+
+**Intent:** Object provides an abstract interface to some type of database or
+other persistence mechanism.
+
+![alt text](./etc/dao.png "Data Access Object")
+
+**Applicability:** Use the Data Access Object in any of the following situations
+
+* when you want to consolidate how the data layer is accessed
+* when you want to avoid writing multiple data retrieval/persistence layers