more flexible image conversion

In Ostro OS (https://ostroproject.org) we have a custom image class which creates a whole-disk image
(https://github.com/ostroproject/meta-ostro/blob/master/meta-ostro/classes/image-dsk.bbclass).

Currently that class is more complex than it should be because it re-implements image compression and conversion to VirtualBox, due to limitations in OE-core's image.bbclass and because we wanted to get rid of the redundant and misleading ".rootfs" suffix in image file names.

These two patches make it possible to simplify the custom code to just the actual dsk image and leverage OE-core for the rest.

The removal of the ".rootfs" suffix would also make sense for OE-core. The first commit can be seen as a first step towards that. It does not change the default, so nothing changes yet, but interested distros or users can already get rid of the suffix by overriding the IMAGE_NAME_SUFFIX variable.

https://bugzilla.yoctoproject.org/show_bug.cgi?id=9076 describes the problem and probably can be considered resolved by these changes.

The following changes since commit 331ad5c5f80044a5e82abca0e87a85b162126411:

mtools: Drop GCONV_PATH manipulation (2016-03-07 12:41:09 +0000)

are available in the git repository at:

git://github.com/pohly/openembedded-core image-conversion
https://github.com/pohly/openembedded-core/tree/image-conversion

Patrick Ohly (2):
image creation: allow overriding .rootfs suffix image.bbclass: support chaining compression (aka conversion) commands

 meta/classes/image.bbclass       | 29 +++++++++++++++---
 meta/classes/image_types.bbclass | 63 ++++++++++++++++++++++------------------
 2 files changed, 59 insertions(+), 33 deletions(-)

2.1.4