Tools: Naming refine: manifest -> partition

The "manifest.manifest" in template is confusing.
It should be "partition.manifest" instead.

This patch does this change to make the templates much more
easy to read and understand.

Also updates the obsolete example code in the document.

Change-Id: Iac0328f353267342187707c405eea57721209443
Signed-off-by: Kevin Peng <kevin.peng@arm.com>
diff --git a/tools/tfm_parse_manifest_list.py b/tools/tfm_parse_manifest_list.py
index 795d90a..8bb1f25 100644
--- a/tools/tfm_parse_manifest_list.py
+++ b/tools/tfm_parse_manifest_list.py
@@ -1,5 +1,5 @@
 #-------------------------------------------------------------------------------
-# Copyright (c) 2018-2020, Arm Limited. All rights reserved.
+# Copyright (c) 2018-2021, Arm Limited. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -62,10 +62,10 @@
 
     Returns
     -------
-    The manifest header list and the data base.
+    The partition data base.
     """
 
-    db = []
+    partition_db = []
     manifest_list = []
 
     for f in manifest_list_files:
@@ -107,7 +107,7 @@
             outfile_name = os.path.relpath(outfile_name, start = source_path)
             intermediafile_name = os.path.relpath(intermediafile_name, start = source_path)
 
-        db.append({"manifest": manifest, "attr": manifest_item, "header_file": outfile_name})
+        partition_db.append({"manifest": manifest, "attr": manifest_item, "header_file": outfile_name})
 
         if OUT_DIR is not None:
             outfile_name = os.path.join(OUT_DIR, outfile_name)
@@ -133,7 +133,7 @@
         memoutfile.write(memorytemplate.render(context))
         memoutfile.close()
 
-    return db
+    return partition_db
 
 def gen_files(context, gen_file_lists):
     """
@@ -246,14 +246,14 @@
     """
     os.chdir(os.path.join(sys.path[0], ".."))
 
-    db = process_manifest(manifest_list)
+    partition_db = process_manifest(manifest_list)
 
     utilities = {}
     context = {}
 
     utilities['donotedit_warning']=donotedit_warning
 
-    context['manifests'] = db
+    context['partitions'] = partition_db
     context['utilities'] = utilities
 
     gen_files(context, gen_file_list)