doc: Reword document titles

This patch attempts to standardise the document titles as well as
adding titles to documents that were missing one. The aim is to
remove needless references to "TF-A" or "Trusted Firmware" in the
title of every document and to make sure that the title matches
with the document content.

Change-Id: I9b93ccf43b5d57e8dc793a5311b8ed7c4dd245cc
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
diff --git a/docs/acknowledgements.rst b/docs/acknowledgements.rst
index 095b5ad..5f2d5bc 100644
--- a/docs/acknowledgements.rst
+++ b/docs/acknowledgements.rst
@@ -1,12 +1,12 @@
+Contributor Acknowledgements
+============================
+
 **Note: This file is only relevant for legacy contributions, to acknowledge the
 specific contributors referred to in "Arm Limited and Contributors" copyright
 notices. As contributors are now encouraged to put their name or company name
 directly into the copyright notices, this file is not relevant for new
 contributions.**
 
-Contributor Acknowledgements
-============================
-
 Companies
 ---------