Add filters for tags and ranges to delete command

[lauft]

Make TimeWarrior's command delete process tags and date ranges

timew delete foo # delete all intervals with tag "foo"
timew delete <date_start> - <date_end> # delete all intervals within range

Open questions:

• What about implicit ranges like

timew delete <day/month/year> # 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

[gkssjovi]

I have created an extension that allow you to do that.

https://github.com/gkssjovi/timewarrior-extensions.git

timew delete $(timew ids TagName :week) or timew delete-tag TagName :day