Feature: Support tagging events / tasks and filtering

[BVengo]

It would be nice to have the ability to add tags to events (e.g. all weather events would be defaulted to have the tag 'Weather'). For my specific requirements, I'd like to tag all university exams or assignments as 'Uni'.

With this feature, a combination of the following could be implemented:

• filtering the event list by tag
• filtering the event list to event-only dates
• filtering the event list by date range (instead of just showing that month)