Added an editable table with the payments

I added Angular and created a html table with editable(ng-model) cells for tags and category. It saves the changes when pressing the 'Save' button. There is currently no way to save individual rows, it saves the entire list.
It would be nice to have a status icon indicating whether you have unsaved changes or not.

Another option would be to save every time the users changes a value, without having to explicitly click the button.