Fix "bad multiple inputs", more cleanup

Parsing from scratch with current master results in "bad multiple inputs" errors due to a conflict between the new input selection and some leftovers of the old input selection ([791ef0/msc_utils_parsing.py#L346](https://github.com/mastercoin-MSC/mastercoin-tools/blob/791ef008e2c6c4ce4615bacc23c378c47ea47593/msc_utils_parsing.py#L346) vs. [b4498e/msc_utils_parsing.py#L309](https://github.com/mastercoin-MSC/mastercoin-tools/blob/b4498e1e5e7ea825f6674f3c4ddf072d5faecd9a/msc_utils_parsing.py#L309)).

This commit fixes this error, but also includes cosmetic and non-consensus relevant adjustments.