Provide r(2+1)d 152-layer models and weights

[daniel-j-h]

Right nowe we only provide the model and weights for r(2+1)d 34-layer which strikes a perfect balance between model size/runtime and accuracy in practise (sorry Kaggle folks).

We should make our code modular so that we can provide e.g. the CSN models or the 152-layered r(2+1)d model (although in practise it is quite heavy for the tiny bump in accuracy).

[bjuncek]

https://github.com/bjuncek/VMZ

hopefully will be merged soon