Restructure Render Args

Currently, there is one argument for everything related to the rendering. Might be good to split this, and define defaults in the config file.

Rendering is down always for train and test. No selection anymore.

render = "none" # ["display", "record", "none"]
render_freq = 5 # first episode of n-th epoch --> define number of epochs
test_display_metrics = [] # list of metrices, maybe two lists are needed for train and test case, because there are different metrices for train and test
train_display_metrics = []