Implement persistent configuration for options

[dimonomid]

Nerdlog supports setting options such as :set timezone=UTC, but it's not much useful because there is no way to persist this configuration across restarts.

While it could be easy to implement it using e.g. yaml configuration file, I'm hesitant of doing that because the longer-term plan is to add Lua scripting support, to be able to have custom message parsing logic etc. Having that, it'll be possible to set options in the script as well (using e.g. file ~/.config/nerdlog/nerdlogrc.lua). But that requires more thought, and so persistence of options is also blocked on that.

Anyway, this ticket is just about persistence of configuration options, one way or the other.

[dimonomid]

It's somewhat mitigated now by having the --set command line flag: ecae528, so one could have an alias for the nerdlog command, setting all the needed option values.