With this change we include more detailed error codes in visualization
output. In order to do so we map TGen transfers/streams to TorCtl
STREAM event details based on source ports and unix_ts_end timestamps.
This code reuses some concepts used in metrics-lib.

Implements tpo/metrics/onionperf#34218.

Implements tpo/metrics/onionperf#40005.

The switch tells OnionPerf to prepend yesterday's date to the analysis
output file.  This new switch is mutually exclusive with --date-filter.

This fixes <https://bugs.torproject.org/29369>.

Previous OnionPerf visualizations were written using PyLab, which is a
relatively low-level visualization library based on matplotlib. PyLab
is the same thing as PyPlot but with some extra shortcuts. However,
using PyLab is discouraged now.

This commit switches all tgen plots to use seaborn, which is a
high-level data visualization library also based on matplotlib. This
commit also uses pandas for underlying data structures in order to
separate data tidying and data visualization.

As a side effect of using pandas, graphed data is now exported to a
.csv file using the same naming scheme as the produced tgen .pdf file.

Implements #33258.

Implements #34224.

Turns out that Tor control log files use \r\n for newlines. When we
open these files without providing a newline parameter, line endings
are translated by Python 3 into '\n' before being returned to the us.
If we do specify a newline parameter, line endings are returned to us
untranslated. We need \r\n as newlines for Stem to recognize and parse
control events.

On the other hand TGen log files use \n as newline, which is why we
need to make newlines configurable.

The tool 2to3 discovered these issues.

Fixes #29367.

closes #34

When exporting tpf files and a date filter is being applied, don't
export downloads that may have ended on the correct date but
started on a previous date.

refs #31

refs #31

closes #30

fixes #20

refs #18

torperf file format update, requested by karsten
https://trac.torproject.org/projects/tor/ticket/17755