Configure() Prompt Improvements

While configuring Embedded Git with do ##class(SourceControl.Git.API).Configure() for the first time with @isc-pbarton , we found a few areas where the prompts could be clarified and improved:

1. 'The system's default mode' prompt should be _before_ the user setting for basic mode, not after. Additionally, the term 'system' here should be replaced with 'Namespace' as this sets basic/expert mode at the _Namespace_ level.
2. 'Branch from which Sync will merge changes, in basic mode': This prompt should not be asked if the plugin is in expert mode.
3. 'Define a namespace-level web application allowing access to multiple git repos across separate namespaces': In reality the purpose of this is to create a web application passthrough allowing you to edit the files in the git repo directly in VSCode, rather than just editing files in the SMP. This should be clarified in the prompt.