Follow XDG Base Directory Specifications

[VinceUB]

Currently, Bastet automatically generates the .bastetrc and .bastetscores files in $HOME. This pollutes the home directory, and doesn't follow the XDG Base Directory Specs.

The specs state that program configuration should be localised to a subdirectory of $XDG_CONFIG_HOME, which defaults to $HOME/.config. In Bastet's case, I think it would make sense to move $HOME/.bastetrc to $XDG_CONFIG_HOME/bastet/bastetrc.

Similarly, user-specific data should be stored in a subdirectory of $XDG_DATA_HOME, which defaults to $HOME/.local/share. In Bastet's case, I think it would make sense to move $HOME/.bastetscores to $XDG_CONFIG_HOME/bastet/scores or something similar.