Removed redundant instance of "output format".

The string "output_format" appeared twice in the
list of input variables in iputfile.py. I removed
one of these instances, as having it twice is
not necessary and confusing.
More gravitas in the legend.

I make the legend appear by default, and I put
it in a nice shadow box.
Added output_format = xml

ATOMPAW 4.x allows the output of pseudopotentials
in a universal xml format. I added this functionality
to inputfile.py.
Modified find_abinit_output --> find_output

The routine was modified to recognize both abinit and xml
output, and then to copy psp file to external directory
following the same pattern as the previous find_abinit_output
routine.
Modified comments to account for 'xml' output.
TYPO: comp_in_xc_keyword -> comp_in_XC_keyword

I think this typo prevented the corresponding variable
from being properly set. The variable is now
set to "comp_in_XC_keyword" throughout the code.
Removed debugging scaffolding.

I had some "print debug" lines, which I used to
find a typo. I removed this code as it is no
longer useful.
New example : Fe
Modified the rc property to handle empty channels.

It is possible to not have any valence states in a channel
For example, Fe: 3d64s2, where 3s23p6 remains in the core, has
no explicit l=1 valence states. Before the present modification,
the code would crash because the rc property tried to zip an
empty array. This has been corrected.
Spurious blank line removed at end of input file.

The last line should be "0", indicating to ATOMPAW
that it is time to shut down. Before this modification,
an extra "\n" introduced a blank line in the input file
before the final "0", which lead ATOMPAW to quit
with an error message. Now, with this spurious blank line
removed, the code quits elegantly.

This has no consequence on the functionality of the code,
as this "problem" only occured when ATOMPAW was about
to quit anyways.
Merge pull request #1 from rousseab/master

New example (Fe), fixed a few typos, and code now outputs in XML, thanks to ATOMPAW 4.x