1) understand file name pattern and modify subset file to follow convention

2) patch header:
- <File_Name>
- <Notes> - maybe add that fle was processed with SMOS-Box version x.x.x
- <Precise_Validity_Start>: acquisition period??
- <Checksum> how is this calculated and_ do we need to recalculate and patch?
- <Header_Size unit="bytes">011122</Header_Size>
- <Datablock_Size unit="bytes">00000367475</Datablock_Size>
- <Product_Location> recalculate and set
- <Total_Num_Grid_Points>: adapt
-  <Data_Set><DS_Size>
-  <DS_Offset>
-  <Num_DSR>
