Add single channel mode feature.

The addition of a single-channel mode implied further modularisation of the component. This commit has broken the component down into the following modules to avoid a huge single source file and to make unit testing easier.

The modules:

- Separation of public and private code
- *types and *defs
- public relay_chn API
- *adapter
- *output
- *run_info
- *core
- *ctl (control)
- *tilt

Closes #957.

.vscode/settings.json

@@ -1,6 +1,23 @@
 {
     "files.associations": {
-        "relay_chn.h": "c"
+        "relay_chn.h": "c",
+        "stdlib.h": "c",
+        "cstdint": "c",
+        "relay_chn_run_info.h": "c",
+        "esp_err.h": "c",
+        "relay_chn_output.h": "c",
+        "relay_chn_core.h": "c",
+        "relay_chn_ctl.h": "c",
+        "relay_chn_tilt.h": "c",
+        "relay_chn_defs.h": "c",
+        "esp_check.h": "c",
+        "esp_event_base.h": "c",
+        "esp_event.h": "c",
+        "queue.h": "c",
+        "relay_chn_priv_types.h": "c",
+        "relay_chn_adapter.h": "c",
+        "relay_chn_types.h": "c"
     },
-    "idf.port": "/dev/ttyUSB0"
+    "idf.port": "/dev/ttyUSB0",
+    "idf.pythonInstallPath": "/usr/bin/python"
 }