This is a fairly substantial change, which adds a new configuration file
to the user's `$RAD_HOME` that includes node configuration, including
the alias, and also makes node aliases required.
When running `rad auth`, the user is now prompted for an alias, which
defaults to `$USER`.
When running `rad self`, the alias is now shown.
If the user runs radicle without a config file, the defaults are loaded,
and `$USER` is used as the alias.
* Return the correct alias from a node announcement, stripping '\0'
bytes.
* Accept `AliasStore` types as references and as owned.
* Store a `null` in the database if the alias received is empty.
Previously, we only sent the announcement when there were external
addresses. But it contains other information like the node alias,
therefore we always send it.
Since the proof-of-work can be expensive to compute everytime, we add
the ability to load the local node announcement from the file system.
We also change the proof-of-work parameters so that they are relaxed
when running in debug mode, instead of when running tests.
Finally, we remove the boolean validation of the PoW. Instead, we store
the work per-node, in the database, to be used in the future in case of
DoS attacks or network congestion.