Simplify the inserted image code

Hi,

I’ve been looking for the solution, but it seems, that nobody made it yet (or it’s really deep burried somewhere).

I’ll try to explain it as simple as possible:
when I insert image into post using the standard editor i get:
<img src="mypath/image.jpg" alt="My Image" title="My Image" width="1024" height="576" class="alignnone size-large wp-image-1234" />
…and I’d love to get rid of this part: class=”alignnone size-large wp-image-1234″

Could someone help me to make a plugin, or edit some files in a way to stop this being included with every picture inserted? …or else I’ll be forced to remove it every time by hand ?? …

Thanks in advance,
Janko