Format doc in utils (partially)

For the wraps method (in __init__), using <BLANKLINE> allows the
docstring to be displayed correctly.
Format doc in utils/data_specs.py (ok?)

I am unsure about the changes here. Using the original version on my
computer, Sphinx was not outputting the "Attributes" sections of class
DataSpecsMapping.

Howewer, it appears in the documentation at deeplearning.net, although
it looks strange. After the small changes I made, I can get Sphinx to
output the doc on my computer, but the format doesn't correspond to that
of the "Parameters" section, nor to that of the "Attributes" section on
deeplearning.net.
Continue formatting documentation in utils
Add utils.rng to documentation

Also minor changes to utils/pooling
Continue formatting doc in utils

Everything in utils is done apart from track_version.py. I will modify
that file at the end.
Format doc for cuda_convnet

Only the files mentioned in pylearn2/doc/alex.txt were modified.

For many classes, there is an enumeration (eg "images, filters and
outputs" in class FiltersActs) in the docstring. I didn't modity these.
Should I?

Just to make sure:
1. Are the parameters "ds", "stride", "start" and "outputs" always
integers?
2. Should there be a doctring for the one-liner functions such as
c_header_dirs, c_headers, c_lib_dirs, etc.?