v1.4.0

Add documentation and manpages.
Highlight: Provide updated API-Document (core documentation) on
https://new-session-manager.jackaudio.org/

Legacy-GUI:
Overhaul look and feel.
Rewrite labels and buttons with unambiguous descriptions.
Protect text-input dialog windows from empty strings, like "Add New Client" or "New Session"
Scale icons, support more icon formats.
Show all icons and buttons when attaching to a running nsmd session
Various small fixes.
Always show correct session name, no matter how the session was loaded or how the GUI was started

nsmd:
NSM_API_VERSION_MINOR from 0 to 1 (1.0 -> 1.1)
Repair nsmd to correctly send client data when running headless and a GUI announces later.
ClientId generation now prevent collision with existing IDs.
nsmd command line option --load-session to directly load one (Berkelder, Rik)
Better detection of clients that failed to launch leads to faster session startup (by 5 seconds)
Users get informed by client-label if an executable is not present on the system or permission denied
Fixed reply for listing sessions from a plain "Done." to proper reply path with empty string as terminal symbol "/reply", "/nsm/server/list", ""
Fix operation reply to last treated client instead to reply to sender (Picot, Mathieu / houston)
/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 )