Convert .ino -> .cpp (#2228)

- general conversion from .ino modules into a separate .cpp files
- clean-up internal headers, place libraries into .h. guard .cpp with _SUPPORT flags 
- fix some instances of shared variables instead of public methods
- tweak build system to still build a single source file via os environment variable ESPURNA_BUILD_SINGLE_SOURCE

code/espurna/rpc.cpp

@@ -0,0 +1,66 @@
+/*
+
+Part of MQTT and API modules
+
+Copyright (C) 2020 by Maxim Prokhorov <prokhorov dot max at outlook dot com>
+
+*/
+
+#include <Schedule.h>
+#include <cstring>
+
+#include "system.h"
+#include "utils.h"
+#include "rpc.h"
+
+bool rpcHandleAction(const String& action) {
+    bool result = false;
+    if (action.equals("reboot")) {
+        result = true;
+        schedule_function([]() {
+            deferredReset(100, CUSTOM_RESET_RPC);
+        });
+    } else if (action.equals("heartbeat")) {
+        result = true;
+        schedule_function(heartbeat);
+    }
+    return result;
+}
+
+PayloadStatus rpcParsePayload(const char* payload, const rpc_payload_check_t ext_check) {
+
+    // Don't parse empty strings
+    const auto len = strlen(payload);
+    if (!len) return PayloadStatus::Unknown;
+
+    // Check most commonly used payloads
+    if (len == 1) {
+        if (payload[0] == '0') return PayloadStatus::Off;
+        if (payload[0] == '1') return PayloadStatus::On;
+        if (payload[0] == '2') return PayloadStatus::Toggle;
+        return PayloadStatus::Unknown;
+    }
+
+    // If possible, use externally provided payload checker
+    if (ext_check) {
+        const PayloadStatus result = ext_check(payload);
+        if (result != PayloadStatus::Unknown) {
+            return result;
+        }
+    }
+
+    // Finally, check for "OFF", "ON", "TOGGLE" (both lower and upper cases)
+    String temp(payload);
+    temp.trim();
+
+    if (temp.equalsIgnoreCase("off")) {
+        return PayloadStatus::Off;
+    } else if (temp.equalsIgnoreCase("on")) {
+        return PayloadStatus::On;
+    } else if (temp.equalsIgnoreCase("toggle")) {
+        return PayloadStatus::Toggle;
+    }
+
+    return PayloadStatus::Unknown;
+
+}