Image plugin commit

Hello!
I've added in the advanced tab of the image plugin the float property. 

I think is very useful to write text next to an image. Until now you can write directly in the style box but it's better with a combo box for non advanced users.

I've puted bigger the maxWidth of the textboxes to have the same sizes in the all properties.

It's very simple but I hope you like it.

Cheers.
Oscar