Draw a calendar grid

The grid can either have 5 or 6 rows, depending on the month. There is not code
yet for determining the number of days in a month, or the weekday the month
begins with. But it works if you set those manually.

Threw away the code that shows the date for now.
Draw the date numbers
Update the README file
Added code to determine the weekday of 1 Jan of any year

This subroutine (weekdayYearStart) computes the weekday of the first day of the
year, and it also determines whether the year is a subroutine. The next step
will be to use this to actually draw the correct calendar for the selected
month.
Highlight the selected day in the calendar

The initial selected day is taken from getTime, which is in the emulator
1997-01-01. Note that the window title is not dynamic yet, so that always says
"Jan 2014".

It is not possible yet to change the selected day.
Show a nice message when clock is unsupported

The message uses corelib's showMessage function. The only option at the moment
is to quit the application, but it may also be possible to fall back to some
standard date.
Use the correct number of days in the month, and add date selection

The highlighted date can now be changed by using the arrow keys. It is not yet
possible to go to another month - the selection then just disappears. Also the
name of the current month is not yet shown.

Also, fixed a stupid bug in weekdayYearStart, where the algorithm only worked
correctly when b was zero, and thus failed in subsequent invocations.
Show the name of the currently active month
Only repaint the entire screen if needed
Make it possible to navigate to other months

At the moment, going back to the previous month does not work as expected if
the current month doesn't have the same amount of days as the previous one.
This should be fixed.
Created a subroutine to compute the weekday of the first day of any month

First, there only was code for computing the first day of a year. Now, the
program shows every month correctly. Only the navigation is still not entirely
correct.