In preparation to support creation of native docker containers the
way docker likes it, the kiwi schema has to be adapted. So far there
was no way to specify additional metadata information for containers.
With this commit a new section called <containerconfig> is provided.
containerconfig is a subsection of the type and only allowed for
the docker image type. This constraint is checked via a schematron
rule. In addition an xslt stylesheet moves the currently existing
container attribute, which was used to set a name for the container,
into the new containerconfig section as name attribute
Indicate if the target disk for oem images is deployed to a
removable device e.g a USB stick or not. This only affects
the EFI setup if requested and in the end avoids the creation
of a custom boot menu entry in the firmware of the target
machine on first boot. This is related to bnc#993130
The attribute allows to specify if the root filesystem should
be set to read-only if it is created as a btrfs snapshot.
The option only has an effect if a btrfs snapshot is used as
root filesystem. Fixes bnc#1000080
