Store the file list sorting mode in GSettings
Store the scanner window mode in GSettings
Store the file extension case mode in GSettings
Store the playlist content mode in GSettings
Store ID3v1 and ID3v2 iconv options in GSettings
Store rename filename encoding in GSettings
Store the process fields option in GSettings
Store disc padding preferences in GSettings
Store ID3v2.4/2.3 preference in GSettings
Store default browse path in GSettings WIP

Still TODO: checking for a valid path. Consolidating validity checks
into one place.