V11

2022/05/17 V11 :    
    > fix issue " Still some CRC errors occur when uploading on SDCard #21 ": remove sevbuf use to fix the last CRC errors and limit 
      to only 1 transfer for sdCard operations (simultaneous transfers leads in CRC errors)  
    > multi transfer enhancement : reduce open/close connection time with 
        - using a static preallocated array of threads (before it was allocated statically when creating the connection) 
        - manually set cpu and priority of transfer threads
    > now use also a small buffer for UL operations (before setting manually CPU and priority, a large buffer was used to let other 
      connections start)
    > tweak the buffers sizes used for DL / UL
      Use 25% DL vs 75% UL of the reserved memory for buffer socket operations (instead of 50/50)
    > This last setting increase DL speeds obtain when multi-transferring. Using a small buffer for upload reduced the "speed displayed" 
      on UL operation (now take the fwrite time into account). 
      This version gives max speeds about 4M/s on both ways but treat a large number of files more quickly.