be more explicit, only exif_transform jpegs, and if mode is not rgb convert it first before thumbnail - fixes BUG-63 no thumbs for GIFs

shared.py

@@ -113,9 +113,10 @@ def SymlinkName(ptype, path, file):
 def GenThumb(fname):
     try:
         im_orig = Image.open(fname)
-        im = ImageOps.exif_transpose(im_orig)
-        bands = im.getbands()
-        if 'A' in bands:
+        if im_orig.format == 'JPEG':
+            im = ImageOps.exif_transpose(im_orig)
+        im = im_orig
+        if im.mode != "RGB":
             im = im.convert('RGB')
         orig_w, orig_h = im.size
         im.thumbnail((THUMBSIZE,THUMBSIZE))