Allow 2-of-2, 2-of-3, 3-of-3 multisig
Filter pay-to-pubkey-hash and multisig outputs
Already taken care of in is_accepted_output
Reference output selection adjustments

- If there are one or multiple outputs to the sending address, only the
first will be ignored for change purposes
- The reference address will be determined by the remaining output with
the highest vout index
Fix script for multisig
Allow change output
Input selection for class B transactions
Fixed spacing
Fetch output based on txid:n
Filter output type in input selection
Catch case with no valid input at all
Seperate output type check, allow multiple Exodus outputs
Handle empty result for tx fetching more properly
Retry to fetch tx, if assertion error
Make sure one valid input exists, move output validation
Define multisig output looser

Already taken care of:
https://github.com/dexX7/mastercoin-tools/blob/015e201f17a2691bb5d9b80c95dc5ca3d2bb6c4e/msc_utils_parsing.py#L371
Adjust, so overall difference is smaller
Fix method names
merge dexx's changes
invalidate non script paytopubkeyhash inputs