Option to make a "contents" path read only

[jvailius]

Problem

If certain notebooks are not intended for editing then the user has to delete those in the browser to go back to the provided version if it was saved to local storage. This can be quite confusing.

Proposed Solution

Optionally configure certain paths in contents as read only so they are never saved to local storage. When the browser is opened those notebooks will always be in the initial state as provided by the server.

[bollwyvl]

The nickel fix: chmod the contents to be read-only on disk before running the build, and the flag will propagate to the generated api/contents/*.json files, which the client app will respect. Or, post-process the contents JSON.

[jvailius]

Thank you, good work around for now. It disables the save button but I can still overwrite the file with "save as..".