Fix typo
Add basic implementation for adding activities

- Until now, an activity are identified (-> grouped) by an individual text
  -> this will be replaced with a reference to a project...
- DB: new table "activities"
- New JS lib: moment.js
- Go app: changes concerning handler funcs + much more
Remove dummy page/code
Adds delete functionality for activities
Order activities by duration (desc)
Add formatted duration (total) to page header
Add initial functionality to change duration of activies.
Refactore adding/saving activities
Rename methods (names unnecessary included context)
Layout activity items on activities page
Show time on progress bar (per activity item)
Merge branch 'activities'