new: allow form.metadata.htitle to override settings sheet form title.

* this accounts for the "Title on Device" form properties setting in the
  ODK Build UI.
* progress on getodk/build#154 .

spec/src/convert-form-spec.ls

@@ -295,6 +295,10 @@ describe 'settings generation' ->
     expect(result[1][0]).toBe(\myform)
     expect(result[1][1]).toMatch(/build_myform_[0-9]+/)
 
+  test 'uses metadata htitle for form title if provided' ->
+    result = gen-settings({ title: \myform, metadata: { htitle: 'override title' } })
+    expect(result[1][0]).toBe('override title')
+
   test 'sanitizes form title' ->
     result = gen-settings({ title: 'Untitled! Test Form' })
     expect(result[1][1]).toMatch(/build_Untitled-Test-Form_[0-9]+/)

src/convert.ls

@@ -176,7 +176,12 @@ convert-question = (question, context, prefix = []) ->
   # return. context is mutated (:/) so does not need to be returned.
   question
 
-gen-settings = (form) -> [ [ \form_title, \form_id ], [ form.title, "build_#{form.title?.replace(/([^a-z0-9]+)/ig, '-')}_#{Math.floor((new Date()).getTime() / 1000)}" ] ]
+gen-settings = (form) ->
+  form-title = if is-nonsense(form.metadata?.htitle) then form.title else form.metadata?.htitle
+  form-id = "build_#{form.title?.replace(/([^a-z0-9]+)/ig, '-')}_#{Math.floor((new Date()).getTime() / 1000)}"
+
+  [ [ \form_title, \form_id ],
+    [ form-title, form-id ] ]
 
 # the main show.
 convert-form = (form) ->