bugfix for tools/extra/parse_log.sh

./tools/extra/parse_log.sh was broken by the recent changes to the training output, in particular by the way test accuracy and test loss are now displayed. caffe.log.test had empty columns where accuracy and loss per iteration were supposed to show up.

previously (training output):
I0828 00:56:34.795725 31294 solver.cpp:177] Test score #0: 0.9319
I0828 00:56:34.795765 31294 solver.cpp:177] Test score #1: 0.173513

now (training output): 
I0831 01:21:36.325670  8457 solver.cpp:302]     Test net output #0: accuracy = 0.9426
I0831 01:21:36.325687  8457 solver.cpp:302]     Test net output #1: loss = 0.152957 (* 1 = 0.152957 loss)

culprit in parse_log.sh:
grep 'Test __score__ #0' aux.txt | awk '{print __$8__}' > aux1.txt
grep 'Test __score__ #1' aux.txt | awk '{print __$8__}' > aux2.txt

Also, fixed a number of typos and updated the script description.