Polish the documentation of appbase.js

Replace the constant App.withMathJax by App.mathJax with is the path to the mathjax script.
Modified accordingly the function to load the library.

Have this information up to date is required by the paging plugin.

the new handler onInit is only execute once.

Load ten record when the paginh plugin is there.

Put in place the standard mechanism for store.
Load the store when it is needed.