User can choose if calc MD5 from decrypted file

At the present moment, if user want use OTA, the function calculate MD5 of the decrypted file, but if file is encrypted from source, could be more useful to know the MD5 of the encrypted file.

Author: zinkett

libraries/Update/src/Update.h

@@ -137,8 +137,9 @@ class UpdateClass {
 
   /*
       sets the expected MD5 for the firmware (hexString)
+      calc_post_decryption if true che update library calc MD5 after decryption, if false the calc is before decryption
     */
-  bool setMD5(const char *expected_md5);
+  bool setMD5(const char *expected_md5, bool calc_post_decryption);
 
   /*
       returns the MD5 String of the successfully ended firmware
@@ -256,8 +257,9 @@ class UpdateClass {
   uint32_t _command;
   const esp_partition_t *_partition;
 
-  String _target_md5;
-  MD5Builder _md5;
+  String _target_md5; 
+  bool _target_md5_decrypted=true;
+  MD5Builder _md5; 
 
   int _ledPin;
   uint8_t _ledOn;