Merge pull request #590 from jkczyz/2020-04-feature-flags

Features module improvements

diff --cc fuzz/src/chanmon_consistency.rs
Simple merge

diff --cc lightning/src/ln/chanmon_update_fail_tests.rs
Simple merge

diff --cc lightning/src/ln/channel.rs
Simple merge

diff --cc lightning/src/ln/channelmanager.rs
Simple merge

diff --cc lightning/src/ln/functional_tests.rs
Simple merge

diff --cc lightning/src/ln/msgs.rs
Simple merge

diff --cc lightning/src/ln/peer_handler.rs
Simple merge

diff --cc lightning/src/ln/router.rs
Simple merge

diff --cc lightning/src/util/test_utils.rs
Simple merge