Added a test in test_NetworkCompare to verify cudnn and exconv, fixed a bug in cudnn_conv in dealing with groups

out = w * input
where w is a parameter of size 1

Change-Id: Ife682d62323ceb1a20cbbf6269421b20a862d888

rebase deconv implementation with develop branch and resolve conflicts with pull#218 commit 45c81a41

This allows user to implement any type of cost by summing over the output of non-cost layers.

Change-Id: Ic55aaabbf0c1299e70b8e48a0effcc91f8f5bd29

* Fix SRL hang when exit.

* Error occurred when enable Async Load in TestDataProvider.
  * It because DataProvider is calling getNextBatchInternal in one thread, and destructing DataProvider in other thread.
  * Add wait routine in DataProvider destructing.
* Also fix another bug, when destructing TestDataProvider and do not read any test data.

Fix #286

* Follow comments, Use mutex is cool!

* Add elementwise math operations
This allows use to use expressions like: y=log(1+exp(x))
Also added unittests for ActivationFunction
* Enforce keyword arguments for non-positional arguments
* Add LogActivation to doc