Added settings validation

Added AliaSqlSettings validation and more detailed error messages to make debugging easier.

So instead of just geting `Error: Object reference not set to an instance of an object.` or tool errors you can gett errors like:
```
Error: AliaSql: ConnectionString not specified or missing ()
Error: AliaSql: DatabaseName not specified or missing ()
Error: AliaSql: ScriptsFolder not specified or missing ()
Error: AliaSql: ScriptsFolder not specified or missing (src/Database/Scripts)
```