Grid dropdown correctly populating database.

	modified:   app/controllers/questions_controller.rb - determine if any new columns need to be built
	in render_grid_fields_partial.

	modified:   app/models/permitted_params_decorator.rb - whitelist for columns.  Add columns attributes
	to question_group whitelist.

	modified:   config/routes.rb - get rid of unnecessary route for grid_dropdown_columns partial.

	modified:   lib/generators/surveyor_gui/install_generator.rb - add column_id to answers.  grid dropdowns
	will need to iterate on both question_id and column_id.

	new file:   lib/generators/surveyor_gui/templates/db/migrate/20140602030330_add_column_id_to_answers.rb -
	add column_id to answers.

	modified:   lib/surveyor_gui/models/question_group_methods.rb - get rid of reject_ifs on accepts_nested_attributes.

	modified:   lib/surveyor_gui/models/question_methods.rb - add writer for question_group_attributes.

	modified:   lib/surveyor_gui/models/question_type_methods.rb - complete process_grid_columns_textbox and pass
	column_id through the chain of builder methods it calls.