Config GUI: activate Save and Test Connection buttons only if input is present

[bpintea]

In case of editing or adding a DSN, the Save and Test Connection should only be activated if there is valid input, as follows:

• the Save button requires a DSN Name and Hostname filled in;
• the Test Connection button requires at least the Hostname field filled in. The delux feature here would be do have validation on the field (hostname or IPv4/6), but this only if there is already some ready to use framework functionality (regexps or building a parser here might be inadvisable).

[codebrain]

We can probably use the Uri parser in .NET to perform some validations for us (agree that writing our own parser is not a good idea!)

https://docs.microsoft.com/en-us/dotnet/api/system.uri.-ctor?view=netframework-4.7.2

[bpintea]

Thank you!