After making the date selector use the brand
new date chooser widget, it is now time to make
it an entry.
This commit, then turns GcalDateSelector into a
GtkEntry subclass, and add all the plumbing that
is necessary to make it work as such.
As a side effect, this commit adds rudimentary
natural language support for parsing dates.
Georges Basile Stavracas Neto
bdac4e4c79