[scripts] fixed stuff related to model selection (and add the latent dim param needed for the original architecture)

[script] change the name of the script displaying training images, fixed default value for start epoch

[scripts] fixed the script to train using Multi-PIE and CASIA: corrected # of ids and start_index in for ID labels, use my own concatenation class

[datasets] made sure that id labels are native python int, since otherwise it could cause problem in the concatenation of datasets

[trainers] add the performance for minibatches in DR-GAN trainer, as well as the ability to save generated samples in HDF5

[trainers, scripts] fixed stuff in the script to train DCGAN (transforms mostly), reflect changes in the DCGAN trainer

[trainers] made sure that the fixed image used for sampling is frontal, save generated samples during training

[architectures] DR-GAN discriminator: added the number of ids as class variables, fixed the size of the output

[architectures, script] added the architecture of the DRGAN, and the script to train it (trainer not done yet though)