configurable output directory for rendered invoices

[tim-heinsohn]

As a detail for the console task: some things would be nice to be configurable (via config file and as parameter).

One thing important to me is the output directory. It should be possible to specify something like

output_dir: "%kernel.root_dir%/data/%%year/%%month"

in the application config to support the monthly accounting (with a folder containing all sent invoices for a period of time, a customer, a project or service).

Thus, those placeholders could be used in config and should be replaced with their actual values by the Console task:

%year
%month
%customer
%project
%service

(%kernel.root_dir% is replaced by Symfony, it default's to app/)