Add option for filesystem-centric editing via a web application

[isc-tleavitt]

It would be helpful if git-source-control had the option to create a web application (say, /git/<namespace>) that doesn't serve files over CSP but does allow editing of source code. This would be like itemsetsourcelink in a CCR context, and would be handy for the following cases:

• Management of files in the git repo on the server via a real IDE (VSCode)
• Handling conflicts where the effect of the conflict is to prevent import into IRIS

Edits to such files via VSCode should trigger appropriate import behavior, and the web application files themselves should have menu options based on the corresponding InternalName (if there is one). It is important that this import only happens for mapped files - as a particularly common use case, there might be an edit of a system default settings file for LIVE that we wouldn't want to import into dev!

This would be controlled by a namespace-level setting; changing it would create/delete the web application as appropriate. The default should be not to create such a web application.

[isc-tleavitt]

This is especially important for HCC because there is a guaranteed need to edit files that don't map to items in the database - most importantly, system default settings and other environment-variant files that are edited in dev but take no effect until test/prod.