Improved handling of Connectionstrings in Configuration Tab

- Added additional warning message indicating when the assumption is made that when a provider is not configured, that Glimpse assumes `System.Data.SqlClient`
- Added error messages in case something went wrong
- Added fallback scenario in case the connection string could not be parsed. The fallback is creating a list of key value pairs from the connection string. The same info as the raw value is shown but in table mode
- It is now possible to obfuscate multiple parts (values of specific keys) in the same connection string
- It is now possible to add additional keys to obfuscate by setting an `AppSetting`. It is not part of the Glimpse configuration but this allows for additional flexibility while not impacting the configuration. For instance

    ```XML
    <add 
        key="Glimpse:ConfigurationTab:ConnectionStrings;KeysToObfuscate"
        value="SomeSpecialKey;SomeOtherSpecialKey"/>
    ```