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/manual_schema.yml

@@ -1,7 +1,6 @@
 type: object
 required:
   - headline
-  - history
   - body
   - manpage_intro
   - manpage_epilogue
@@ -10,8 +9,6 @@ additionalProperties: false
 properties:
   headline:
     type: string
-  history:
-    type: string
   body:
     type: string
   manpage_intro: