Make Project.thumbnail an Image, not a Costume.

This is a *mostly* backwards-compatible change.

kurt/__init__.py

@@ -185,7 +185,7 @@ def __init__(self):
         """:class:`dict` of global :class:`Lists <List>` by name."""
 
         self.thumbnail = None
-        """A screenshot of the project. May be displayed in project browser."""
+        """An :class:`Image` with a screenshot of the project."""
 
         self.tempo = 60
         """The tempo in BPM used for note blocks."""
@@ -305,7 +305,7 @@ def copy(self):
 
         p.variables = dict((n, v.copy()) for (n, v) in self.variables.items())
         p.lists = dict((n, l.copy()) for (n, l) in self.lists.items())
-        p.thumbnail = self.thumbnail.copy() if self.thumbnail else None
+        p.thumbnail = self.thumbnail
         p.tempo = self.tempo
         p.notes = self.notes
         p.author = self.author

kurt/scratch14/__init__.py

@@ -115,7 +115,7 @@ def load(self, fp):
                 name = 'thumbnail',
                 form = thumbnail,
             )
-        self.project.thumbnail = self.load_image(thumbnail)
+        self.project.thumbnail = self.load_image(thumbnail).image
 
         # stage
         self.load_scriptable(self.project.stage, self.stage)
@@ -149,7 +149,8 @@ def save(self, fp, project):
         self.stage = self.UserObject("ScratchStageMorph")
 
         # project info
-        thumbnail = self.save_image(self.project.thumbnail)
+        thumbnail = self.save_image(
+                kurt.Costume("thumbnail", self.project.thumbnail))
         self.info = {
             'author': self.project.author,
             'comment': self.project.notes.replace("\n", "\r"),