make App.open_for_* look more like io.open

Dependencies

• [2] 3ZTODUBQ formatting
• [3] 7CLGG7J2 test: autosave after any shape
• [4] AD34IX2Z couple more tests
• [5] AVTNUQYR basic test-enabled framework
• [*] 3QNOKBFM beginnings of a test harness

Change contents

• replacement in app.lua at line 305
  [3.1512]→[3.1512:1613](∅→∅),[3.1613]→[3.2592:2636](∅→∅),[3.2592]→[3.2592:2636](∅→∅),[3.2636]→[2.62:79](∅→∅),[2.79]→[3.2652:2656](∅→∅),[3.2652]→[3.2652:2656](∅→∅)
  − return {

  − lines = function(self)

  − return App.filesystem[filename]:gmatch('[^\n]+')

  − end,

  − close = function(self)

  − end,

  − }
  [3.1512]

  [3.7391]
  + if App.filesystem[filename] then

  + return {

  + lines = function(self)

  + return App.filesystem[filename]:gmatch('[^\n]+')

  + end,

  + close = function(self)

  + end,

  + }

  + end