website: Make latest release (1.7) be default manual (#3130)

Fixes issue with confusion about features that has not been
released yet.

Move deveopment manual.yml to dev/manual.yml
Symlink manual.yml to v1.7/manual.yml
Refactor to share history header with links to other manual versions.
Change man.test and man page generation to use dev/manual.yml

Related to #3078 #3127

docs/build_manpage.py

@@ -209,7 +209,7 @@ def dedent_body(body):
 
 def convert_manual_to_markdown():
     f = StringIO()
-    manual = load_yml_file("content/manual/manual.yml")
+    manual = load_yml_file("content/manual/dev/manual.yml")
     f.write(manual.get('manpage_intro', '\n'))
     f.write(dedent_body(manual.get('body', '\n')))
     for section in manual.get('sections', []):