Tags should be done.

In tag_dev the following features have been developed:
* new log entries can include tags (syntax:``"Log" @tag @another_tag``)
* refactors the display code: now logs are reconstructed and the same log_display function is used to print logs in all cases.
* ``--view-all`` and ``--last-X`` options may now be followed by a filter parameter such as a tag
* the total elapsed time for a list result is computed and printed at the end