feat!: configuration file system (#17)

- initial file format is TOML
- lots of refactoring, most notably the CLI argument structures
- added CLI options `--show-config` and `--config-files`
- renamed CLI options --ipv4, --ipv6 to --address-family 4|6  (short
  args `-4` and `-6` unchanged)

.vscode/launch.json

@@ -7,15 +7,15 @@
         {
             "type": "lldb",
             "request": "launch",
-            "name": "Debug executable 'qcpt'",
+            "name": "Debug executable 'qcp'",
             "cargo": {
                 "args": [
                     "build",
-                    "--bin=qcpt",
-                    "--package=qcpt"
+                    "--bin=qcp",
+                    "--package=qcp"
                 ],
                 "filter": {
-                    "name": "qcpt",
+                    "name": "qcp",
                     "kind": "bin"
                 }
             },
@@ -25,16 +25,16 @@
         {
             "type": "lldb",
             "request": "launch",
-            "name": "Debug unit tests in executable 'qcpt'",
+            "name": "Debug unit tests in executable 'qcp'",
             "cargo": {
                 "args": [
                     "test",
                     "--no-run",
-                    "--bin=qcpt",
-                    "--package=qcpt"
+                    "--bin=qcp",
+                    "--package=qcp"
                 ],
                 "filter": {
-                    "name": "qcpt",
+                    "name": "qcp",
                     "kind": "bin"
                 }
             },

.vscode/tasks.json

@@ -4,7 +4,7 @@
 		{
 			"type": "cargo",
 			"command": "doc",
-			"args": ["--no-deps"],
+			"args": ["--no-deps", "--locked"],
 			"problemMatcher": [
 				"$rustc"
 			],