Currently 'listfunds' lies, a teensy eeinsy bit, in that it doesn't list
all of the funds in a wallet (it omits reserved wallet UTXOs). This
change makes the reserved outputs visible by listing them in the
'outputs' section along with a new field, 'reserved', which denotes the
UTXO's state
Changelog-Changed: JSON-RPC: `listfunds` 'outputs' now includes reserved outputs, designated as 'reserved' = true