Display day headers for each day in the week
Make expenses deletable

This change adds a delete "button" to each expense allowing the expense
to be removed.
Allow new expense records to be created

This adds an add button to each day which, when clicked upon, causes a
new edit row to be displayed. The editing takes a time, amount,
description and comment with validation on the time and amount.

There are still a few thing that can be improved here, such as:
* Making the date editable
* Constraining the time (i.e. -1 becomes 23 and sets the date to the day
  before, 20:70 becomes 21:10, etc)
* Constraining the amound to <10000, currently it will just error.
* If there is an error saving then an alert will show.