improve wording of help strings and outputs

amongst other things explain why 'available' is called 'available'

mpsd-software.py

@@ -378,7 +378,9 @@ def get_available_toolchains(mpsd_release: str) -> List[str]:
 
     # summarise toolchains found for use, and show packages provided for each
     # package_set:
-    print_log.info(f"MPSD software release {mpsd_release}")
+    print_log.info(
+        f"MPSD software release {mpsd_release}, AVAILABLE for installation are"
+    )
     print_log.info("Toolchains: \n    " + "\n    ".join(sorted(toolchain_list)))
     print_log.info("Package sets:")
     for package_set in package_sets:
@@ -1038,13 +1040,13 @@ def main():
     )
     subparsers.required = True
     list_of_cmds = [
-        ("available", "Show toolchains available"),
-        ("prepare", "Prepare the environment for installation on the disk"),
+        ("available", "Show software available for installation"),
         ("install", "Install a software environment"),
         # ("reinstall", "Reinstall a software environment"),
         # ("remove", "Remove a software environment or toolchains from an environment"),
         # ("start-new", "Start a new software environment version"),
-        ("status", "Show the status of the software environment"),
+        ("status", "Show status: what is installed?"),
+        ("prepare", "Prepare installation of MPSD-release (dev only)"),
     ]
     for cmd, help_text in list_of_cmds:
         subp = subparsers.add_parser(cmd, help=help_text)