GSoC 2016 - Adding ALIASES for tutorial (#7041)

* GSoC 2016 - Adding toggle files to be used by tutorials.

Add a toggle option for tutorials.
* adds a button on the HTML tutorial pages to switch between blocks
* the default option is for languages: one can write a block
for C++ and another one for Python without re-writing the tutorial

Add aliases to the doxyfile.
* adding alises to make a link to previous and next tutorial.
* adding alias to specify the toggle options in the tutorials index.
* adding alias to add a youtube video directly from link.

Add a sample tutorial (mat_mask_opertaions) using the developed aliases:
* youtube alias
* previous and next tutorial alias
* buttons
* languages info for tutorial table of content
* code referances with snippets (and associated sample code files)

* Removing the automatic ordering.
Adding specific toggles for cpp, java and python.
Move all the code to the footer / header and Doxyfile.
Updating documentation.

doc/mymath.js

@@ -1,4 +1,4 @@
-
+//<![CDATA[
 MathJax.Hub.Config(
 {
   TeX: {
@@ -15,3 +15,4 @@ MathJax.Hub.Config(
   }
 }
 );
+//]]>