Somewhat related to https://jira.xwiki.org/browse/CONFLUENCE-441, idea from @Josue-T

if one migrates a Confluence space whose key is FAQ with the default settings, one will write into the FAQ space, and even partially rewrite the FAQ application (at least its home page).

This is a bit dangerous. We should probably have a list of spaces, that would also include the Blog application, the XWiki space, Sandbox and other well known spaces and warn against such imports.

Note that this is not the same as checking if something is already present at the target space, because we should probably warn even if those applications are not (yet) installed. Though warning that one is going to overwrite an existing space would be a useful feature itself.