Use both pagegenerators and local generator

When the script has a local generator, it can be inserted at the
beginning of the list of generators used by the generator factory.

This is especially useful so that filters may be applied to the
script supplied generator.

Change-Id: I492673ce69c77df9ed697271c7c7e8a9c6fc055d
Merge "Use both pagegenerators and local generator"