create a checksum file before each transfer

Before each file transfer

• created a md5 checksum file, with the same file name as the original and appended extension .md5
• include in the transfer the .md5 file

The goal of this new feature, is to later on, when the data file (stored in PD) is "picked up" by Aiflow or a script, its integrity can be checked against its adjacent .md5 file.