Don't hardcode config path

[lambdadog]

I'm packaging Dolphin with Nix and packages installed with Nix are installed read-only. I believe I'll be able to work around everything else, but short of patching Dolphin (which I will do for the short-term) it would make my package very user unfriendly if the config path can't be passed as an argument or environmental variable.

I imagine there are many other situations that this would be a useful feature as well.

[lunaisnotaboy]

Three years too late, but I am planning on adding this to Dolphin.