[IMP] doc: rewrite part of module structure and js references guidelines
[IMP] doc: rewrite part of module structure and js references guidelines

This commit
 * removes deprecated guidelines for static file and assets struture;
 * fixes some typo and mistakes;
 * correctly links JS guidelines section;
 * adds a running example to ease understanding;
 * adds missing section about security files;
 * adds text blocks for each directory to show directly the
   expected result of each section;
 * perform some rewording;

Thanks to @pedrobaeza for its review.

Task-1817988
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo