Filter logs by month/week/day

[xyzshantaram]

etu log --timesheet is a pretty cool concept, but we can extend it further to grouping sessions by week/mth etc.

example:

week 1 ("implement timesheet functionality" and 2 other sessions)

but probably as a table.

The displayed session should be the longest one in that week, probably.

[xyzshantaram]

By default, log would output a per session log but you could also group by day/week/month (what timesheet does) with --days, --weeks, --months.

Filtering by day/week/month could be accomplished by --day 1 or --day 1-15.