[Feature Request] Add date formats

[loseth]

Add a date (Y, M and D) functionality to the Markdown link, something like this:

[%YYYY-MM-DD  %TITLE](%URL) // ISO (only one that sorts in a sensible manner btw)
[%MM/DD/YYYY  %TITLE](%URL) // US 
[%DD-MM-YYYY  %TITLE](%URL) // European

The easiest would be to take the current date and use that.
But the hard and super useful thing would be to extract the creation date from the article itself. That would be a time saver!

Anyway, great extension! :-)