Minor corrections for jupyter notebooks

[NeoNatural]

Hi, I am Jack. Please see the points below:

1. MNEPython/ICA.ipynb. Within In[3], the raw_resmpl.filter is applied after resampling. It might be better to swap the order.
2. MNEPython/EventRelatedFields.ipynb. Within In[15], the baseline correction is applied to a copy of evoked_left, and thus does not affect the plot_topo below. Also can be seen in the figure that some channels are with non-zero baseline.
3. MNEPython/DICS.ipynb. Within In[12], the same variable 'stc_aRvsL' is assigned repeatedly with two different expressions. Oscar suggested renaming the first one as 'stc_cRvsL'.