added disable the generation of conv_full_patch_stack_padded directly in GpuConv to test the hard coding of more parameter.

small fix. python don't seam to like that we put the default value of an argument to be the result of a fct call to another module.

new config system based on the execution of theano/config.py. Changed all call to os.getenv to use this file and put the config from gof/utils.py in the new file.

-pass verbose and version to new op generated by ConvOp.grad()

always register local_elemwise_fusion, but not in fast_run by default. Allow the test to work and test it event if not enabled.

added a fct to return the instance of the default mode. It check that it exist and raise an informative error if it don't exist.