refactor: move carrier plugins around

data/source/decoder/plain_1.c

@@ -0,0 +1,3 @@
+    for (int n=0; n<{{PAYLOAD_LEN}}; n++) {
+        dest[n] = supermega_payload[n];
+    }

data/source/decoder/xor_1.c

@@ -0,0 +1,5 @@
+    // Single byte XOR key
+    for (int n=0; n<{{PAYLOAD_LEN}}; n++){
+        dest[n] = supermega_payload[n];
+        dest[n] = dest[n] ^ {{XOR_KEY}};
+    }

data/source/decoder/xor_2.c

@@ -0,0 +1,5 @@
+    // Multibyte XOR
+    char *key = "{{XOR_KEY2}}";
+    for ( int i = 0; i < {{PAYLOAD_LEN}}; i++ ) {
+        dest[i] = supermega_payload[i] ^ key[i % 2];
+    }