ivi-shell: bring back reference weston.ini
In commit d8e09afc ("tests: Convert ivi-shell-app-test.c to use
weston_ini_setup
") the reference weston.ini for the ivi-shell was removed,
because it is not required by the test anymore.
The reference weston.ini still has value as an example for the ivi-shell and how the ivi-shell-user-interface has to be configured. Retrieving this information from the test case is not intuitive. Furthermore, the file is still referenced by the ivi-shell/README, and the configuration_data for generating the file was not fully removed.
Bring back the reference weston.ini for the ivi-shell and, while at it, cleanup the configuration_data() to define only keys that are actually used in weston.ivi.in.