Also gived info on how to give name to variables.

bugfix in gpu convolution on the gpu. The bug as created in revision f57050592a51 the 26 january 2010.

print a warning about the move of theano/sandbox/conv.py. We import the new version to don't break stuff for some time.

* moved sandbox/conv.py to tensor/nnet/conv.py
* created tensor/signal/conv.py which implements generic 2D convolution (i.e.
traditional signal processing definition) + tests
* added tensor/nnet/tests/speed_test_conv.py which contains Fred's speed tests
for ConvOp
* added appropriate documentation to sphinx library docs

moved theano.compile.mode.default_{mode,linker,optimizer} to theconfig system as {mode,linker,optimizer}.

Also added that when config.mode is Mode, ProfileMode or DebugMode, mode.get_default_mode return this mode initilized with config.linker and config.optimizer.