CHANGELOG formatting and announce XDG Change for next release

CHANGELOG

@@ -1,4 +1,17 @@
-1.4.1 / 2021-01-15
+#Changelog
+Format: Double ## for a version number followed by a space, ISO-Date, Semantic Versioning:
+## YYYY-MM-DD major.minor.patch
+Two empty lines before the next entry.
+Contributors notice after the change (LastName, FirstName / nick)
+
+
+## 2021-01-15 1.4.1
+WARNING: Next scheduled release (2021-04-15) will switch the default session dir to XDG Data Path.
+Prepare to either
+1) Move old Session to the new root directory
+2) Symlink "~/NSM Sessions" to the new root directory
+3) use the nsmd --session-root commandline argument.
+
 nsmd:
  Command line option --quiet: Suppress messages except warnings and errors
 
@@ -6,7 +19,8 @@ Legacy-GUI:
  Fix manpage description and usage with the correct executable name
  Fix resizing to very small and back. ( / TheGreatWhiteShark )
 
-1.4 / 2020-07-15
+
+## 2020-07-15 1.4.0
 Add documentation and manpages.
 
 Legacy-GUI:
@@ -30,19 +44,19 @@ nsmd:
  /nsm/gui/session/name send consistent session name/relative-path pair to the annouced GUI, no matter how the session was loaded.
 
 nsm.h
- :optional-gui: support to nsm.h, for other applications to include and use. (Meyer, Hermann / brummer )
+ :optional-gui: support to nsm.h, for other applications to include and use. (Meyer, Hermann / brummer)
 
 
-1.3.2 / 2020-06-20
+## 2020-06-20 1.3.2
 Rename new-session-manager executable to nsm-legacy-gui to prevent future confusion.
 
 
-1.3.1 / 2020-06-20
+## 2020-06-20 1.3.1
 Add header copyright even to unchanged files to adhere to stricter packaging requirements.
 Meson can now switch off individual executables and will stop/error when trying to build without dependencies.
 
 
-1.3 / 2020-06-17
+## 2020-06-17 1.3.0
 Rebranding to "new session manager"
 Upstream GUI tools "non-session-manager" and "nsm-proxy" converted to standard FLTK instead of a custom toolkit
 Changed build system to meson
@@ -51,15 +65,15 @@ Simplified file structure
 Fix compiler warnings.
 
 
-1.2.1 / 2020-04-19
+## 2020-04-19 1.2.1
 Current state of upstream Non Session Manager v1.2 including unreleased /nsm/gui/session/root
 
 
-1.2.0 / 2017-07-08
+## 2017-07-08 1.2.0
 Last release of Non-Session-Manager.
 Commit 1904aba516341287ac297cefbbcd185f643e5538
 
 
-1.1.0 / 2012-03-03
+## 2012-03-03 1.1.0
 Initial release of Non-Session-Manager.
 https://non.tuxfamily.org/wiki/2012-03-03%20Release%20Announcement%20v1.1.0