Pasting images introduces spaces and changes styles

[bpieber]

To reproduce:

1. Copy an image outside Cuis.
2. Open a StyledTextEditor.
3. Switch the paragraph style to Heading 1.
4. Paste it.
5. The paragraph style switches to Normal. Before and after the images are spaces. Move the caret with the cursor keys left and right. Note that the character style switches back and forth from "-none-" to "-none- (n)"