This is needed as we get software instances by their reference and not
their relative urls

slapos_jio_api_style: Add related key to be able to search instance from host compute node reference

* NotFound Errors are now handled by API

Can replace the following SlapTool calls:
* softwareReleaseError
* availableSoftwareRelease
* buildingSoftwareRelease
* destroyedSoftwareRelease

See merge request !455