Allow partial filename searches

[jontwo]

Partial searches during restore only apply to whole parts of the path, but should also include partial name matches. Something like:

def get_filename_index(s1, l2, exact=True):
    ...
    except ValueError:
        if not exact:
            global wildcard_matches
            for m in [f for f in l2 if fnmatch.fnmatch(f,'*{}*'.format(s1))]:
                if m not in wildcard_matches:
                    wildcard_matches.append(m)
        return None

and

    logger.warning('%s not found' % filename)
    if wildcard_matches:
        logger.info('some similar files were found though\n%s' % wildcard_matches)

This won't change the files restored, but will tell users what they could be searching for.