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/migrate.cpp

@@ -0,0 +1,67 @@
+/*
+
+MIGRATE MODULE
+
+Copyright (C) 2016-2019 by Xose Pérez <xose dot perez at gmail dot com>
+
+*/
+
+#include "settings.h"
+
+void _cmpMoveIndexDown(const char * key, int offset = 0) {
+    if (hasSetting({key, 0})) return;
+    for (unsigned char index = 1; index < SETTINGS_MAX_LIST_COUNT; index++) {
+        const unsigned char prev = index - 1;
+        if (hasSetting({key, index})) {
+            setSetting({key, prev}, getSetting({key, index}).toInt() + offset);
+        } else {
+            delSetting({key, prev});
+        }
+    }
+}
+
+// Configuration versions
+//
+// 1: based on Embedis, no board definitions
+// 2: based on Embedis, with board definitions 1-based
+// 3: based on Embedis, with board definitions 0-based
+// 4: based on Embedis, no board definitions
+
+void migrate() {
+
+    // Update if not on the latest version
+    const auto version = getSetting("cfg", CFG_VERSION);
+    if (version == CFG_VERSION) return;
+    setSetting("cfg", CFG_VERSION);
+
+    switch (version) {
+        // migrate old version with 1-based indices
+        case 2:
+            _cmpMoveIndexDown("ledGPIO");
+            _cmpMoveIndexDown("ledLogic");
+            _cmpMoveIndexDown("btnGPIO");
+            _cmpMoveIndexDown("btnRelay", -1);
+            _cmpMoveIndexDown("relayGPIO");
+            _cmpMoveIndexDown("relayType");
+            // fall through
+        // get rid / move some existing keys from old migrate.ino
+        case 3:
+            moveSettings("chGPIO", "ltDimmerGPIO");
+            moveSettings("myDIGPIO", "ltMy92DIGPIO");
+            moveSettings("myDCKGPIO", "ltMy92DCKGPIO");
+            moveSettings("myChips", "ltMy92Chips");
+            moveSettings("myModel", "ltMy92Model");
+            moveSettings("chLogic", "ltDimmerInv");
+            moveSettings("ledLogic", "ledInv");
+            delSetting("lightProvider");
+            delSetting("relayProvider");
+            delSetting("relays");
+            delSetting("board");
+            // fall through
+        default:
+            break;
+    }
+
+    saveSettings();
+
+}