Modernization

[Absolucy]

• Use thiserror over failure - cleaner code.
• Use flume instead of std::mpsc - better performance, 100% safe
• Use the rust-crypto crates (md-5, sha-1, sha2) over crypto-hash - slightly more complex code, but one less openssl dependency (sadly, mysql still pulls in openssl)
• Get rid of all the extern crates
• Use serde with the "derive" feature over serde_derive
• Update mysql to 20.0
• Make the file_read/append/write used buffered IO, write/append will ensure that filesystem metadata is synchronized.

[spookydonut]

@aspenluxxxy conflicts

[Absolucy]

@spookydonut fixed