documentation: added a tutorials subsection, added firstSteps tutorial to the index

doc/index.rst

@@ -2,11 +2,12 @@ Welcome to open62541's documentation!
 =====================================
 
 .. toctree::
-   :maxdepth: 2
+   :maxdepth: 3
    :hidden:
 
    building
    datatypes
+   tutorials
 
 `OPC UA <http://en.wikipedia.org/wiki/OPC_Unified_Architecture>`_ (short for OPC
 Unified Architecture) is a protocol for industrial communication and has been

doc/tutorials.rst

@@ -0,0 +1,17 @@
+Tutorials
+=========
+
+First steps with open62541
+------------------------------
+
+:doc:`tutorial_firstSteps`
+
+Contents:
+
+* Checking out the stack
+
+* Creating a minimal user-defined server
+
+* Working with amalgamated files
+
+* Compiling built-in server and client examples