Some web sites have buggy utf8 encoding or not use utf8.
We don't have to be strict, we want a wide coverage.

A bug was introduced by sorting the cache content. Resulting of destroying
the cache object and replace it with a simple dict with no saving.

- Support upgrade
- Refactorise code

Since last major update, a package failure stops the whole sync.
If a package check fails, skip it

Instead of an int vs str error

It's basically a report with a call to sync

Static files are now under a directory in xdg directories (config or cache)

New paths:
$XDG_CONFIG/packages.conf
$XDG_CONFIG/sendmail.conf
$XDG_CACHE/packages.conf

Doesn't compare versions, let that to new mode

KISS++

Archversion now use a new cache format which store upstream and downstream
ersions (with timestamp)

cache is updated by calling the sync command

This option allow to use a regex to exclude upstream versions before trying to
find the last one. Useful to exclude rc* version from a list without building
a complex regex_version.

no more avc list config but avc config
no more avc list cache but avc cache
no more avc list modes but avc modes