Support configuring Onedriver

[jstaf]

Although I was trying to have a one-size-fits-all approach where no one would even need to configure anything, there are some legitimate settings we need to support, including:

• Changing the cache directory
• Ignoring certain types of files/setting up an ignore list
• Disabling/enabling management of KDE's Baloo ignore list
• Setting the on-disk cache size (We don't even support this yet...)
• Different Azure app registrations.

I think the best way to support this would be to configure things via YML (no one hates it, it's very easy to understand, and widely used), and have the GUI configure things via the same YML file. I looked into libyaml and it looks like a nightmare to parse things in C, so honestly this seems like a good opportunity to just take the plunge and rewrite the GUI in Go (then the two packages can share code better).

[jstaf]

Onedriver can now be configured via ~/.config/onedriver/config.yml. I still need to create GUI for configuration.