NR: General tidy up - @seealso @knownissue spacing

NR: General tidy up - @seealso @knownissue spacing

No new information added. Trying to make @seealso sections follow CG policy
including line breaks for consistent visual layout in *.itely files.

Notation Reference only:
Made sure all existing @seealso entries were
i. In the correct order as per the CG
ii. Each @seealso was labelled correctly (i.e. 'Extending LilyPond'
instead of just 'Extending' - as per CG).
iii. Correct punctuation marks at the end of each line entry
iv. Made line breaks between each section consistent (one line space
after main sections). Kept one line space between @seealso and @knownissues.
Made sure two line breaks before next @node. Any @cindex have line space
either side of entry. Removed line space between @seealso and @knownissues
and their respective text entries.
v. Removed @c sections that contained empty @seealso entries
that were just 'placeholders' for the 'future' - as this isn't
standard practice.

[Graham Percival, 2012-03-11 19:20:53]

LGTM, please push directly to staging.

[pkx166h, 2012-03-11 20:20:20]

On 2012/03/11 19:20:53, Graham Percival wrote:
> LGTM, please push directly to staging.

committer	James Lowe <pkx166h@gmail.com>	
Sun, 11 Mar 2012 20:16:43 +0000 (20:16 +0000)
commit	80340bdefc128536c79733d8c6f3467d91b01f72

Thanks,