KISS++

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

cache is updated by calling the sync command

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

Previously update mode never call upstream check function and only use cached
data.

Now it always call upstream check and only save it if -S is omitted

Short version is still the same

To keep the rules of using binary name of the package in the config file,
we grab the pkgname[0] of the bash array. This is done to stay compatible with
archweb.

As bash 4.2.x doesn't export array to env (well know bug). We add a custom
export as string the first field of pkgname array as pkgname0.

This follow a PEP (don't remember number) to improve compatibility accross
distro.

This command allow archversion to quickly update package to its last upstream
version.

Our error exceptions are now catched globablly and __str__ method describe
the issue

Oups?
http://lists.gnu.org/archive/html/automake/2003-09/msg00132.html

This will avoid to run make every time a fix is provided in archversion (dev only)

This is not the same behaviour of argparse than in 2.7 python. I guess
there is a bug.