Resolve "Clarify that Type 0x03 and 0x83 refer to bip47 specifically"

Closes #1

See merge request !8

Specify that decimal to string conversion for hash and emoji calculation should be done in big endian.

Adding token aware versions of the payment data types to allow wallets with token support to use cash accounts with confidence amongst other wallets with token support.

Revert "Change name to identifier in the lookup result."

See merge request !7

This reverts commit 0e9621f7

Test vectors snippets

See merge request !5

Emergent Reasons authored Mar 05, 2019 and Jonathan Silverblood committed Mar 05, 2019

- especially change confusing name combination of payment code and payment data

address and account impersonation attack

See merge request !6

UPDATE: op_return-prefix-guideline.md URL link.

See merge request !4

Spec fixes

See merge request !3