add-on-template_installation.xml - reindenting
add-on-template_installation.xml - use "add-on" textdomain

sync the file content with Factory (skelcd-control-openSUSE-LangAddOn package)
renamed add-on-template_installation.xml -> add-on-installation.xml

it's used in the language add-on as it is (without any modification),
thus removing the "template" from the name
updated changes and the version
Merge pull request #3 from yast/sync_add-on

Update the language add-on control file