Security Guide: Markup of links

The guide does not use markup of links at all, I've started adding
markup to the first chapters. I've also did some minor cleanups I
noticed.

Patch set 2:
Diane, thanks for the review, I've followed all your suggestions.

Patch set 3:
I've fixed the name of the OpenStack Compute Adminstration Guide
everywhere in my patch set.

Patch set 4:
Fix whitespace

Patch set 5:
Fix remaining chapters

Change-Id: I3c11aab2bafadd7f2ee3742fbfcaa7f937102d0d
Merge "Security Guide: Markup of links"