tree-wide: clean up --help texts a bit

This cleans up and unifies the outut of --help texts a bit:

1. Highlight the human friendly description string, not the command
   line via ANSI sequences. Previously both this description string and
   the brief command line summary was marked with the same ANSI
   highlight sequence, but given we auto-page to less and less does not
   honour multi-line highlights only the command line summary was
   affectively highlighted. Rationale: for highlighting the description
   instead of the command line: the command line summary is relatively
   boring, and mostly the same for out tools, the description on the
   other hand is pregnant, important and captions the whole thing and
   hence deserves highlighting.

2. Always suffix "Options" with ":" in the help text

3. Rename "Flags" →  "Options" in one case

4. Move commands to the top in a few cases

5. add coloring to many more help pages

6. Unify on COMMAND instead of {COMMAND} in the command line summary.
   Some tools did it one way, others the other way. I am not sure what
   precisely {} is supposed to mean, that uppercasing doesn't, hence
   let's simplify and stick to the {}-less syntax

And minor other tweaks.

src/activate/activate.c

@@ -332,9 +332,9 @@ static int help(void) {
         if (r < 0)
                 return log_oom();
 
-        printf("%s [OPTIONS...]\n\n"
-               "Listen on sockets and launch child on connection.\n\n"
-               "Options:\n"
+        printf("%s [OPTIONS...]\n"
+               "\n%sListen on sockets and launch child on connection.%s\n"
+               "\nOptions:\n"
                "  -h --help                  Show this help and exit\n"
                "     --version               Print version string and exit\n"
                "  -l --listen=ADDR           Listen for raw connections at ADDR\n"
@@ -347,6 +347,7 @@ static int help(void) {
                "\nNote: file descriptors from sd_listen_fds() will be passed through.\n"
                "\nSee the %s for details.\n"
                , program_invocation_short_name
+               , ansi_highlight(), ansi_normal()
                , link
         );