Pull Request for release 0.9.0beta1

Simplify warn.ignore_bug_before parameters.
Rewrite "cudnn" to "cuDNN".

Small update in vision state (change version from 0.9.dev5 to 0.9.0beta1).

Update .mailmap
Update NEWS_DEV.txt
Tranfer old content of NEWS.txt to HISTORY.txt
Copy content of NEWS_DEV.txt into NEWS.txt
Update setup.py, doc/conf.py, doc/index.txt
Update warn.ignore_bug_before parameters in configdefault.py and doc/library/config.txt
Fix typo in doc/internal/how_to_release.txt

Cusolver using Cholesky decomposition for symmetric matrices

Broadcasting tutorial

Change default of round() to be as NumPy and warn about it.

Add C code to RoundHalfToEven op.

by hardcoding the rounding instead of relying
on NumPy functions, so that this op should work
on CPU and on GPU.

Tests (CPU and GPU) passed on my computer, let's
see if jenkins/travis are ok with that.

Merged previous work implementing stack trace copy over and tests for…

(as I have changed the headers list).

Add a deprecation message to the old backend.

Initialize the blas kernels when creating the contexts.

Add user warning to prevent issue #5143

mixed