Make use of DimeReportBundle

[quafzi]

DimeReportBundle could guide users to create invoices.

DimeReportBundle already generates timeslice lists based on a customizable filter. So that is, what we probably need for invoices. So it would be great to use that to provide data for invoices:

• add checkboxes to report lines
• add a button to trigger invoice creation

That way, we wouldn't need that much frontend tasks for DimeInvoiceBundle and these two bundles could concentrate on what they are supposed to do.