'ObservedMRDLayer' predict and plot_latent

[vcuculo]

1. It seems that predict method is missing from the ObservedMRDLayer object.
   When m.predict() is called and the loop reaches the MRD layer it results in

AttributeError: 'ObservedMRDLayer' object has no attribute 'predict'

2. When trying to plot the latent space, instead, it tries to import a missing module
   

   PyDeepGP/deepgp/layers/mrd.py

   Line 168 in 4ec944f

   from GPy.plotting.matplot_dep import dim_reduction_plots

😕

[vcuculo]

ok, for point 1. this seems to do the job
phuselab@a4675ba?diff=unified#diff-58960237dbea25ce1641c87b9c47bf27