show scriptSig signature hash types in transaction decodes. fixes #3166

show scriptSig signature hash types. fixes #3166

Please give this a look and let me know if you'd like it changed or if I mis-understood the issue request.

The fix basically appends the scriptSig signature hash types, within parentheses, onto the end of the signature(s) in the various "asm" json outputs. That's just the first formatting idea that came to my mind.

Added some tests for this too.
Thanks for the code review. Guarding that lookup with CheckSignatureEncoding I believe prevents that case, but you're right, I did not realize or intend for the [] operator to act that way. So, it'll be safer to make the change that you propose in-case someone changes CheckSignatureEncoding to act differently in the future. I'll get that done today and re-squash the commit.