Add locals add and remove subcommands

- `locals add` adds a local (unintroduced) certificate for encryption.
- `locals remove` removes/deacivates a local certificate.
- Overall cleanup

src/cli/cli_args.rs

@@ -94,8 +94,8 @@ pub struct IntroducerAddCommand {
 
     #[clap(
         long = "cert-file",
-        help = "Import certificate from CERT_FILE and declare it as introducer.",
-        value_name = "CERT_FILE",
+        help = "Import certificate from <FILE> and declare it as introducer.",
+        value_name = "FILE",
         conflicts_with = "cert"
     )]
     pub cert_file: Option<String>,
@@ -159,8 +159,9 @@ pub enum LocalsSubcommand {
 )]
 pub struct LocalsAddCommand {
     #[clap(
-        long = "cert",
-        help = "Certificate to add."
+        long,
+        help = "Import a certificate from <FILE>.",
+        value_name = "FILE",
     )]
     pub cert_file: String,
 }
@@ -168,12 +169,12 @@ pub struct LocalsAddCommand {
 #[derive(Parser, Debug)]
 #[clap(
     name = "locals_remove",
-    about = "Certificate to remove.",
+    about = "Disable a Certificate.",
 )]
 pub struct LocalsRemoveCommand {
     #[clap(
         long = "cert",
-        help = "Certificate to removed."
+        help = "Certificate to be removed."
     )]
     pub cert: String,
 }