Added convolutional autoencoders to the autoencoders notebook

- Simplified a little the way convolutional nets are constructed
- Added convolutional autoencoders to the [autoencoders notebook](http://nbviewer.ipython.org/gist/khalednasr/c78cfebb99d72a06622a)
- Disabled INFO logging in the neuralnets notebooks, to prevent them from cluttering buildbot 

@lisitsyn, Please take a look