Make it always a number; this makes the JSON request specification
simpler. We allowed a number since v0.10.1.
(reserve=True is the default anyway, so usually it can be omitted:
reserve=False becomes reserve=0).
Changelog-Deprecated: JSON-RPC: `fundpsbt`/`utxopsbt` `reserve` must be a number, not bool (for `true` use 72/don't specify, for `false` use 0). Numbers have been allowed since v0.10.1.
Any file in this directory which is executable and whose name only
consists of alphanumeric characters, space, '.', '-' or '_' will be
automatically loaded when lightningd starts (unless suppressed with
commandline options).