Combine Loggo() and loggo.events

[interrogator]

• Remove loggo.events, which has very similar code to logme anyway
• Add its functionality to the line where Loggo is instantiated with config: loggo = Loggo(config, called='custom message --- {timestamp}, {call_signature}')
• Change internal names pre -> called etc now that they are exposed to user
• If user explicitly passes called=None, no logs for calling. Otherwise, existing defaults are used
• Document available formatting strings in README
• Move error_alert_level to config, default 50
• build_string no longer needed, timestamp and trace can be in the default format strings

This will reduce size of codebase, which is good.

[hukkin]

Done and merged here: https://github.com/bitpanda-labs/loggo/pull/81