Based on suggestion by Pieter Wuille <pieter.wuille@gmail.com> at
https://github.com/bitcoin/bitcoin/pull/12119#issuecomment-357982763
After #12119, the NONE output type was overloaded to refer to either an output
type that couldn't be parsed, or to an automatic change output mode. This
change drops the NONE enum and uses a simple bool indicate parse failure, and a
new CHANGE_AUTO enum to refer the change output type.
This change is almost a pure refactoring except it makes RPCs reject empty
string ("") address types instead of treating them like they were unset. This
simplifies the parsing code a little bit and could prevent RPC usage mistakes.
It's noted in the release notes.
Change all instances of validateaddress to getaddressinfo since it seems that
no test actually uses validateaddress for actually validating addresses.
-BEGIN VERIFY SCRIPT-
find ./test/functional -path '*py' -not -path ./test/functional/wallet_disable.py -not -path ./test/functional/rpc_deprecated.py -not -path ./test/functional/wallet_address_types.py -exec sed -i'' -e 's/validateaddress/getaddressinfo/g' {} \;
-END VERIFY SCRIPT-
