Use correct site for pagegenerators

GeneratorFactory accepted a site parameter, but did not pass it to
many of the generators it instantiated.

Also delay loading of the site, if not specified, until in handleArg
after which pywikibot.handle_args has processed the global command
line arguments.

Plus PEP257 fixes.

Bug: 72120
Change-Id: Ibef4116e6894e722f1e95d092b4f178d91d7760c
MySQLPageGenerator fails due to wrong classname

The generator tries to compare against pywikibot.site.Site,
which doesnt exist.  Use BaseSite instead.

Bug introduced in Aug 2013 - 2e35403.

Bug: 72127
Change-Id: I4876b53baebf656e196682c203c45e65551f200e
Merge "Use correct site for pagegenerators"