v0.4: more usable and more recovery paths!

This fourth release brings support for descriptors with multiple recovery paths as well as several
usability improvements in the GUI around signing devices management, and more.

Features

• We now support having multiple recovery path in a descriptor.
• We now support more general descriptors: multisigs in the primary or any of the recovery paths
  henceforth aren't required to use multi() anymore and the maximum number of keys per spending
  path is thereby lifted.

GUI-specific

• You can now re-register the descriptor on a hardware signing device in the settings.
• You can now change the alias of each of the signers from the settings panel.
• At signing time we now warn you if the descriptor is not registered on the signing device.
• The signer alias is now displayed along with its type when signing.
• You can now connect to a running daemon without having to provide a path to its configuration,
  provided it is using the default location for its data directory (or --datadir is used).
• The GUI will now log to a installer.log file at the root of the datadir during installation, and
  to a <network>/liana-gui.log when running. In case of crash, this will contain a backtrace.
• During installation we now check the connection to bitcoind.

Fixes

• We won't error when parsing of descriptor with a 1-of-N multisig as primary path.
• We won't error at startup if our watchonly wallet is loading on bitcoind. Instead, we'll wait for
  completion of the previous loading attempt.

GUI-specific

• Blank addresses aren't treated as duplicates when creating a transaction.