rename 'scripts' directory to 'launchers'

[johrstrom]

While we refactored the Launcher models and controllers recently, we left this one piece standing - the scripts directory itself. We should change the name of this directory before the 4.0 release.

This directory here:

ondemand/apps/dashboard/app/models/launcher.rb

Lines 12 to 14 in 1b076a8

	def scripts_dir(project_dir)
	Pathname.new("#{project_dir}/.ondemand/scripts")
	end

I deferred this because there are likely a lot of tests that need to be updated.

[euler-room]

fixed in #3922