added UserImportFile worker file

Conflicts:
	app/controllers/user_import_files_controller.rb
	app/models/user_import_file.rb
added user_encoding to UserImportFile

Conflicts:
	app/controllers/user_import_files_controller.rb
	app/models/profile.rb
	app/models/user_import_file.rb
	spec/dummy/db/schema.rb
	spec/fixtures/user_has_roles.yml
	spec/fixtures/user_import_files.yml
	spec/models/user_import_file_spec.rb