[IMP] l10n_es: Complete refactorisation of l10n_es

[IMP] l10n_es: Complete refactorisation of l10n_es, removing duplicities of the three current charts using charts inheritance. Details of the work done in this blog post (in spanish):

http://serviciosbaeza.com/blog/43-refactorizacion-de-l10n-es-para-openerp-v7