Add LogLevel configuration

[X9VoiD]

Default LogLevel is set to Info.

The configuration file is loaded only during boot sequence of daemon, and reconnection of UX (why do we still have two separate instances of everything in OpenTabletDriver.Desktop/Plugin).

Generated file looks like this:

# The minimum level of log messages to output. Valid values are Debug, Info, Warning, Error, Fatal
loglevel = "Info"

This supersedes #2176.

[InfinityGhost]

Why is this using TOML? This could easily be done in the Settings class.

[X9VoiD]

Things are already logged before settings is loaded.

[gonX]

I'm not sure if I like the TOML idea either. How about using env vars?

[gonX]

@X9VoiD respond pls

[X9VoiD]

Env vars is fine, will update at some point.