Revert "replaced use of depricated module scrapy.settings with the method get_project_settings()"

This reverts commit 1b4d14c8f635b28d5f72d37f924c4e71d71520ca.

Calling `get_project_settings()` generates a new independent Settings
object that doesn't contain the overrides passed by command line
arguments, for example.

Proper port would require implementing the from_crawler() class method
and making sure the settings object is passed to all internal objects
(probably breaking some minor backwards compatibility).