Merge pull request #6 from valenciahn/master

Comunicacion con ws exitosa
XML Factura

Se agregan cambios para generar XML de la factura
Se agregan cambios faltantes para generar factura
Merge branch 'master' of https://github.com/yehoshuasm/turtle

Conflicts:
	Forms/Invoicing/ConceptsForm.Designer.cs
	Forms/Invoicing/ConceptsForm.cs
	Forms/Invoicing/InvoicingForm.Designer.cs
	Forms/Invoicing/InvoicingForm.cs
	Forms/MenuForm.Designer.cs
	Model/Invoice.cs