Improve error handling

[Klaus-Tockloth]

v, err := state.GetPath(key)
if err != nil {
	log.Fatalf("error [%v] at state.GetPath()", err)
}

Error message if the 'key" doesn't exists:

2022/11/03 11:48:12.922025 main.go:124: error [github.com/ulfox/dby/db.(*Storage).GetPath#163
: github.com/ulfox/dby/db.(*SQL).getPath#154
: the given key [MissingKey] does not exist] at state.GetPath()

The error message is difficult to handle because the error cause 'does not exist' is not wrapped. So it's difficult to distinguish 'does not exist' from any other possible error.

[ulfox]

Yea, makes sense, it is confusing right now. I will have a look on this when I find some time after work