slice should be only slice index, but it's display name

[r03ert0]

Only the slice index (0 based) should be used for indexing data, and the display name only for display. We have https://microdraw.pasteur.fr/F117_P32_Nissl/F117_P32_Nissl.json&slice=54 (NSA 57) instead of https://microdraw.pasteur.fr/F117_P32_Nissl/F117_P32_Nissl.json&slice=53.

And the DB entries look like:

{
    "fileID" : "https://microdraw.pasteur.fr/F117_P32_Nissl/F117_P32_Nissl.json&slice=54 (NSA 57)",
    "user" : "katjaq",
    "project" : "FIINDv2",
    "Hash" : "-5edfaa41",
    "annotation" : {
        "path" : ["..."],
        "name" : "Region 1",
        "uid" : "9d819dcde390d8"
    },
    "backup" : true
}

We should use slice indices exclusively, and to cleanup the database accordingly (plus, the current method maybe allows for xss attacks!)