Question editor bug - fixed problem adding more than one row.

Found that when entering more than one row, all but one is squashed.
That's because the attribute numbering is stuck at 0 for all new rows.
Added call to the replace_idx method in surveyor_gui.js.  This will
renumber all attributes, which is necessary for the update to correctly
process the parameters.

	app/controllers/questions_controller.rb: changed the
	render_partial_picks method.  Name now render_answer_fields_partial.
	When adding rows, use blank Question attributes and build empty
	answer.

	app/views/questions/_answer_fields.html.erb: add simple_fields_for
	statements.

	app/views/questions/_form.html.erb: added back render _picks.

	app/views/questions/_picks.html.erb: took out simple_fields and
	render.  _answer_fields now added using ajax.

	config/routes.rb: renamed render_picks_partial route to
	render_answer_fields_partial.

	lib/assets/javascripts/surveyor_gui/surveyor_gui.js: modified
	code to hide/show #answer_choice (instead of adding/deleting via
	ajax).  Modified to add/delete _answer_fields partial with ajax.

	lib/assets/stylesheets/surveyor_gui.sass: hide #answer_choice by
	default.