Rename crawled files to their hash to avoid duplicating files.

[xshill]

At the moment, PyRDP names files crawled with its file crawler the same name as they have on the victim. To avoid duplicating files, we could name them according to their hash.

This would pose a problem since one of the file crawler's features is to recreate the remote system's file hierarchy when crawling files. However, there is a fix for that in Linux: store the file somewhere, name it after its hash, and when creating the hierarchy, create a symlink to that file. For example:

files
    - d40ea526169cb99ec8b81ff4d60ebd78
victim
    - data
        - sensitive
            - secrets.txt (symlink to d40ea526169cb99ec8b81ff4d60ebd78)

For Windows, we can't have symlinks but we could fallback to the original behaviour of saving the files without their hash.

[xshill]

See issue #270