Default database directory location

[mikfire]

If you start from a brand new configuration, we create ~/.config/brewtarget with all the right defaults, including user_data_dir set as an empty string.

On the next run of brewtarget, that empty string is taken as meaning cwd and you get a completely different database.

I kind of dig it as a developer, because I get the database.sqlite file in my build directory, which makes rapid prototyping rapid. But I'm thinking it may surprise somebody.

[mikfire]

Oh. That's fun.

When starting from scratch, Brewtarget::initialize() calls Brewtarget::getConfigDir() which creates a QDir with a path of ~/.config/brewtarget. At this point, the path doesn't exist because we haven't created it. canonicalPath() returns an empty string, which causes user_data_dir to be saved as an empty string. Things go weirdly after that.