Web application refactor

We no longer keep track of duration values on the week objects. Instead,
the duration and parser duration values are knockout (pure) computed
observables.

Also, the day objects now use computed observables for the display
duration value.

This commit also includes a change that makes the parser duration column
display the duration if there are no explicit durations in the diary
file.

This commit includes an update to knockout 3.2 so that the new and
improved pure computed observables can be used.