Change pagegenerator tests to dry tests

Adjust NamespaceFilterPageGenerator such that the site parameter
is only needed if namespaces contains strings that are not integers.

Update many of the pagegenerators tests to work using a dry site.

Change-Id: I25ee1f17f6c0478da43c8c2e1576b69f0140b737
Merge "Change pagegenerator tests to dry tests"