GO FR: Improve signature

I thought of this once but decided to not post it, thinking I was, perhaps, too demanding, but my colleague had exact same thought today :)

I had a simple idea of how to improve this without much redesign.

HTML signatures are not simple. When you go into account settings, you have these fields:

- Signature
- template
- edit template

That first signature is a textual one. So we could label it "textual signature"

Template would be called "choose template/html signature"

and the button "edit templates" or so would be called "edit template/html signature".

This way, usability is better and more chances of one knowing how to create a signature without having to read our faq. :)