Improving SLU for number of transfers

Adding more utterances to bootstrap and more options to HDC-SLU.
Merge pull request #63 from UFAL-DSG/num_transfers

Improving SLU for number of transfers.
Added discriminative pretraining and lowered memory requirements in FFNN VAD training.
Merge branch 'master' of github.com:UFAL-DSG/alex
Update of installation instructions.
Update INSTALL.rst
Update INSTALL.rst
Update INSTALL.rst
Update INSTALL.rst
Fixes and small changes when deploying Alex on a virtual machine without CUDA.
"Merge branch 'master' of github.com:UFAL-DSG/alex
NN VAD added option for the number of hidden layers.
Merge branch 'master' of github.com:UFAL-DSG/alex

Conflicts:
	alex/tools/vad/train_voip_nn_theano_sds_mfcc.py
Create download_models.py
x flag
Speeding up NN VAD training.
Fix in gradient size
Dockerfiles.
Added docker buildall script.
Added discriminative pretraining option to NN VAD training. Refactoring.