merge 2 myfs

[despiegk]

• specify the backend storage system(s) to be used for the resulting myfs
• the merge will make sure that the blobs are on the backend storage system (so merge will copy the required blobs to requested backend if not there yet)

scenario

• there is myfs1, myfs2
• we create myfs3 which will be on storage locations a & b
• myfs3 = myfs1:/something + myfs2:/. in other words we can merge a subfolder into other place of ...

remarks

• use the bulk upload/download feature to do it fast

[rawdaGastan]

Created before #53

[rawdaGastan]

Progress

• flists can be merged into one flist
• the output flist is uploaded to the server
• we can download the flist content using download-dir command with flist hash
• an issue is faced but solved now