This commit adds support for OCI images. Most of the docker related
code is reused for OCI classes and Docker classes have been refactored
so now they are a splecialization of the OCI classes. It is done this
way since KIWI internally only uses OCI format to operate with
containers, therefore docker images just differ from OCI images by
the way they are packaged or unpackaged.
Instead of creating a simple tarball the tools umoci and skopeo
from the docker tool chain are used to create official docker
images. Along with those tools more information to describe a
container has been added to the schema. A complete container
setup now consists of the following elements
<type image="docker">
<containerconfig name="..." maintainer="..." user="..." workingdir="...">
<entrypoint execute="command">
<argument name="option"/>
...
</entrypoint>
<subcommand execute="command">
<argument name="option"/>
...
</subcommand>
<expose>
<port number="..."/>
...
</expose>
<volumes>
<volume name="..."/>
...
</volumes>
<environment>
<env name="variable" value="value"/>
...
</environment>
<labels>
<label name="..." value="..."/>
...
</labels>
</containerconfig>
</type>
nose is no longer maintained, thus we have to move to another
testing system. This commit updates the tox setup and all tests
to use pytest instead of nose.
