Add filters for tags and ranges to delete command

Make TimeWarrior's command `delete` process tags and date ranges
```
timew delete foo # delete all intervals with tag "foo"
timew delete - # delete all intervals within range
```
Open questions:
- What about implicit ranges like
```
timew delete # delete all intervals within given day/month/year
```

- What does "interval is within range" mean?
-- Start time of interval is within range?
-- End time of interval is within range?
-- Interval is enclosed by range (both start and end time within range)?

See also #126, #125, #124 which are related to this issue

Start with the `delete` command and review related issues #124, #125, and #126. Resolve whether implicit date ranges are supported and define what it means for an interval to be within a range before implementation. Done means `timew delete` can process tags and the agreed date-range semantics.

Written by the indexing model from the issue text.