Allow to set up Cloudooo scripting.

The enable-scripting parameter allows to specify a LibreOffice script to be applied before saving the document, as per cloudooo@a09d87af. If false (the default), an exception will be raised instead.

This is also enabled as ooo_enable_scripting in the generic.cloudooo recipe.

This also adds two SlapOS integration tests classes to test the functionality:

• TestScripting requests an instance with scripting enabled, and tests the scripting functionality.
• TestScriptingDisabled tests that scripting fails if it is not enabled explicitly.