safe load of yaml in xpdAcq

[sbillinge]

also check for this in xpdAn, SHED and wherever.

[st3107]

I was thinking that this unsafe_load was used for a reason so I didn't change it. Now I know that this is only a historical problem. I will change this in the new release.

    @classmethod
    def from_yaml(cls, f):
        maps = yaml.unsafe_load(f)