Arbitrary limitation that images dir must be under /home

[rdmark]

We currently have an arbitrary limitation that forces the default images dir to be a subdir to /home --

cpp/piscsi/piscsi_image.cpp

string PiscsiImage::SetDefaultFolder(const string& f)
{
    if (f.empty()) {
        return "Can't set default image folder: Missing folder name";
    }

    string folder = f;

    // If a relative path is specified, the path is assumed to be relative to the user's home directory
    if (folder[0] != '/') {
        folder = GetHomeDir() + "/" + folder;
    }
    else {
        if (folder.find("/home/") != 0) {
            return "Default image folder must be located in '/home/'";
        }
    }

I think it's time to remove this limitation and allow users to define the default images dir anywhere on the file system. F.e. they may want to mount external storage media under /mnt and use that for images storage. (Although the mount point could certainly be under /home but that is not a good practice IMHO)

[rdmark]

Discarding after discussion in PR