Rationale: it can be convenient (especially when running on cluster) to set
the compile directory dynamically, within the python program.  The new get/set
methods make this possible, whereas before it was impossible.

in Prepend_scalar_to_each_row.perform, if the output is not of the good size, we try to resize it. Otherwise we create a new one.

added file new_ops where we should put ops that are not in the core of theano. It is better to have all ops in the same place, so that we can find other ops made by other people.