We observed lines in our logs where the timestamp field was still
respecting the timestamp regexp, so the line was not reported as
invalid, but parsing such timestamp caused a ValueError in
_matchToDateTime

The beginning of line was:
127.0.0.1 - - [14/Jul/2017:127.0.0.1 - - [14/Jul/2017:09:41:41 +0200]

Which uses `[14/Jul/2017:127.0.0.1 - - [14/Jul/2017:09:41:41 +0200]` as
timestamp, so this fail the simple .split() used to separate timestamp
and timezone.

Added a minimal test case to reproduce this specific problem.

Use a decorator to not indent the whole function.

This change introduces a (minor) parameter value backward-incompatibility.

There is no standard unquoted URL encoding (=charset), so do not unquote
to just handle ASCII. Fixes various UnicodeDecodeError failures, at the
cost of decreased report readability.

This causes errors and solves nothing.

Do it while parsing, so (for example) day splitting happens at midnight in
chosen timezone instead of midnight in source timezone.
When no timezone is provided, use input's times verbatim.
DST changes cause artefacts in graphs (double or zeroed hour).
Also, display used timezone in generated page.

Depending on input, some state files can starts with ".", and are not
matched by "state/*".

Turns out, builtin works fine with shlex with python 3.

Allows shell expansion (ex: "@~/foo.cfg" cannot be expanded, "@ ~/foo.cfg"
can be).

Replace with quarterhour, do not change plot period.

Makes error plot more readable when there are very few errors.