Use python3 for executing upload.py, drop --end

The core has moved to Python3, so search for that instead of using
obsolete Python2.

Remove the --end argument since it is no longer needed by upload.py

src/ESP8266LittleFS.java

@@ -209,7 +209,7 @@ private void createAndUpload(){
     File espota = new File(platform.getFolder()+"/tools");
     File esptool = new File(platform.getFolder()+"/tools");
     String serialPort = PreferencesData.get("serial.port");
-    String pythonCmd = PreferencesData.get("runtime.os").contentEquals("windows") ? "python.exe" : "python";
+    String pythonCmd = PreferencesData.get("runtime.os").contentEquals("windows") ? "python3.exe" : "python3";
     String uploadCmd = "";
 
     //make sure the serial port or IP is defined
@@ -225,15 +225,15 @@ private void createAndUpload(){
       uploadCmd = uploadPyFile.getAbsolutePath();
     }
     // Find python.exe if present, don't fail if not found for backwards compat
-    String[] paths = { platform.getFolder()+"/tools", platform.getFolder()+"/tools/python", PreferencesData.get("runtime.tools.python.path") };
+    String[] paths = { platform.getFolder()+"/tools", platform.getFolder()+"/tools/python3", PreferencesData.get("runtime.tools.python3.path") };
     for (String s: paths) {
       File toolPyFile = new File(s, pythonCmd);
       if (toolPyFile.exists() && toolPyFile.isFile() && toolPyFile.canExecute()) {
         pythonCmd = toolPyFile.getAbsolutePath();
         break;
       }
     }
-    // pythonCmd now points to either an installed exe with full path or just plain "python(.exe)"
+    // pythonCmd now points to either an installed exe with full path or just plain "python3(.exe)"
 
     //find espota if IP else find esptool
     if(serialPort.split("\\.").length == 4){
@@ -327,13 +327,13 @@ private void createAndUpload(){
       System.out.println("[LittleFS] port    : "+serialPort);
       System.out.println("[LittleFS] speed   : "+uploadSpeed);
       if (!uploadCmd.isEmpty()) {
-        System.out.println("[SPIFFS] python   : "+pythonCmd);
-        System.out.println("[SPIFFS] uploader : "+uploadCmd);
+        System.out.println("[LittleFS] python   : "+pythonCmd);
+        System.out.println("[LittleFS] uploader : "+uploadCmd);
       }
 
       System.out.println();
       if (!uploadCmd.isEmpty()) {
-        sysExec(new String[]{pythonCmd, uploadCmd, "--chip", "esp8266", "--port", serialPort, "--baud", uploadSpeed, "write_flash", uploadAddress, imagePath, "--end"});
+        sysExec(new String[]{pythonCmd, uploadCmd, "--chip", "esp8266", "--port", serialPort, "--baud", uploadSpeed, "write_flash", uploadAddress, imagePath});
       } else {
         sysExec(new String[]{esptool.getAbsolutePath(), "-cd", resetMethod, "-cb", uploadSpeed, "-cp", serialPort, "-ca", uploadAddress, "-cf", imagePath});
       }