BF: cmd_pytest -- pass locals() as well into execfile

otherwise all the loaded/defined locally dss, ds would not be seen
inside:

$> echo print(dss[0]) > /tmp/1.py

$> PYTHONPATH=$PWD bin/pymvpa2 pytest -e /tmp/1.py -i /tmp/1.hdf5
ERROR: name dss is not defined (NameError)

after the fix:

$> PYTHONPATH=$PWD bin/pymvpa2 pytest -e /tmp/1.py -i /tmp/1.hdf5
<Dataset: 48x6@float64, <sa: chunks,targets,train>, <fa: nonbogus_targets>, <a: bogus_features,lastpartitionset,nonbogus_features,train_set>>
BF/DOC: pass over cmd_'s -- minor typos, fixes, safe-guards, use of -i in example cmdlines (might have not been exhaustive)
BF: tried to fix badexternals failure on travis, not sure if that would be all

also removed import of h5save from cmd_preproc, seems to be not used explicitely (run
just retuns the ds)
Merge pull request #5 from yarikoptic/cmdline_modular

various minor fixes/tune ups while was passing through cmdline submodule