Printing weekly data graph.

We print something like this:

    $ Timestat -w
    31 xxxxxxxxxx
    32 xxxxxxxxx
    33 xxxxxxxxxxxx
    34 xxxxxxxx
    35 xxx
    36 xxxxxxxxxxxxxxxx
    37 x
    38 xx
    39 xxxxxxxxxxxxxxxxxxxxxx
    40 xxxxxxxxxx

A line `n` + " " + "x" * k` indicates that I worked k hours on week n.
Removing trailing whitespace.
Added option to query current activity

This -c option is most handy if the output is displayed in the shell
prompt.
--ignored-activities option added
Merge commit 'attis/current'

Conflicts:

	timestat.py
Action files may have comments in them

Comment lines are started with a hashmark.
Bugfix: weekly_sum more than one years

Previosly the --weekly_sum option did not work correctly when there were more
than one years in the action file.