Rewrite of 4.1.11 Attachments

Well-structured original to begin with, but this section also contained many sentences that were either descriptions, procedures or a combination of both.(For example, the paragraph 'Transmission Format' in the original). I took a stricter approach in separating that.

The Rationale-paragragh is also aimed at non-techies and as such contained much too complex content. This was placed elsewhere in the section.

Took out he unclear term "common requirements", this does not define well what the requirements relate to (statements, attachments, LRS, client?) and put those under the header "requirements for statement streams that include attachments".

As with other rewrites, please check meticulously and place comments before pulling.