refactor(error): improve error handling

Addresses issue kindelia#247.  (more to come later)

kindelia_core:

* removes all unwrap() from net.rs
* defines error enums in net.rs: ProtoCommError and ParseAddressError
* return Result from affected fn in net.rs
* change IPV6 panic!() to unimplemented!()
* accept addr arg for Node::new() so it can avoid returning Result
* update test and bench as necessary

kindelia:

* add dep on anyhow crate
* return anyhow::Result from config methods
* return anyhow::Result from main methods, including main()
* return anyhow::Result from FileInput::read_to_string()

kindelia/Cargo.toml

@@ -47,7 +47,7 @@ serde_json = "1.0"
 
 # Events API
 tokio = { version = "1.19.1", features = ["sync"] }
-
+anyhow = { version = "1.0.66", features = ["backtrace"] }
 
 [dev-dependencies]
 assert_cmd = "1.0.1"