Add script to check package installability

The obs-installability script uses the dose-distcheck tool to check
for package installability across the different images types.

It checks for the following group of packages lists:
```
target: for packages to be installed on minimal images
hmi + target: for HMI packages to be installed on target images
development + target: for tools used by OBS and developers
sdk + development + target: for packages to be installed on basesdk images
sdk + development + hmi + target: for packages to be installed on sdk images
```
And it translates the dose-distcheck YAML output to the JUnit format so
that Jenkins can understand it.

This commit also includes the Dockerfile and Jenkisfile for integration.

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>