Remote management of input files

Content-based file management

extern int query_files(
    const char* project_url,
    const char* authenticator,
    int batch_id,
    vector<string> &md5s,
    vector<string> &paths,
    vector<int> &absent_files
);

extern int upload_files (
    const char* project_url,
    const char* authenticator,
    int batch_id,
    vector<string> &md5s,
    vector<string> &paths
);

Per-user file sandbox