Relative HTML doc paths in doc links works locally, but breaks on
crates.io. Luckily, we can now use explicit full paths and rustdoc
will resolve them for us.
If the ChannelManager never receives any blocks, it'll return a default blockhash
on deserialization. It's preferable for this to be an Option instead.
Refactor synchronize_listeners by pulling out a function returning the
validated block header of a BlockSource's best chain tip. This is needed
when a node is started from scratch and has no listeners to sync.
The implementation of chain::Listen for ChannelMonitor required using a
RefCell since its block_connected method required a mutable borrow. This
is no longer the case since ChannelMonitor now uses interior mutability
via a Mutex. So the RefCell is no longer needed.
Add a utility for syncing a set of chain listeners to a common chain
tip. Required to use before creating an SpvClient when the chain
listener used with the client is actually a set of listeners each of
which may have had left off at a different block. This would occur when
the listeners had been persisted individually at different frequencies
(e.g., a ChainMonitor's individual ChannelMonitors).
