Maintain display_order when switching between group based and solo questions on question editor.

Also pass text too.
	modified:   app/controllers/questions_controller.rb - accept
	display_order from params if prev_question not known.

	modified:   lib/assets/javascripts/surveyor_gui/surveyor_gui.js -pass
	question.text /  question_group.text when switching back and forth
	between group and solo question_types.

	modified:   lib/surveyor_gui/models/question_methods.rb - minor rearrangement
	in order of appearance of methods.  No functional effect.
Get group questions to seamlessley change question types.
	modified:   app/controllers/question_groups_controller.rb - after
	saving a question group, destroy the original question whose type
	was switched to group.  I.e., if starting with text question 121,
	switching to group_default, adding some questions, and saving, remove
	question 121, so there is not a text question remaining after the switch.

	modified:   app/views/question_groups/_group_inline_field.html.erb -
	remove hidden field for id.

	modified:   lib/assets/javascripts/surveyor_gui/surveyor_gui.js - fix error
	in retrieving question_id, and check to see if the original question can still be found
	after editing a group and returning from ajax call.  The original question
	will be gone if user switched from non-group
	question to a group question.  In this case, instead of refreshing just the question on
	the surveyform, refresh the entire section.

	modified:   lib/surveyor_gui/surveyforms_controller_methods.rb - add a check to replace_question
	to ensure the question can be found. If not, return inline text with error message.