this also fix bad display of all changelog in verbose mode

we now have a changelog command, no needs to overload list output

we can now set a minimal installsystems version in your description
install will not be able to read those images

Add tarfile from python 2.7.2

This allow method add in Tarfile to have filter parameter.
This give us filter capa on file to include.
Should be removed when python 2.7 will be the minimum version

Because we roolback to python 2.6 requirment, we need to ship.

Signed-off-by: Sebastien Luttringer <sebastien.luttringer@smartjog.com>

is new have now an force option to overwrite existing images

This allow and easy double extracting without needs to delete it before

is new try to instanciate the new created object. But it doesn't pass validation...

tarfile module fail to extract tarball with utf8 filenames when destination is an unicode
string. We need to convert dest as utf-8 string to restore an expected behaviour

Add a changelog file inside isimage with a custom format which allow
image creator to quickly show update between images

Add a isversion field inside isimage which tell which version of installsystems was used to build image

We now use PipeFile to handle complex file type and compute md5 and filesize.

This commit add the following features in installsystems:
- A download progress bad
- check size before download
- check size after download
- check md5 after download

$ is del description
Error: not a gzip file

$ is del description
Error: Unable to open image description: not a gzip file

This is a better way of doing things. This help to have a better display of
where is causing latency

This fix is a workaround taking a class gzipstream from redhat (GPL2)
which allow gzip class to be not seekable.
Since python 3.2, gzip module is now not seekable. Until we swith to version
we should use this hack