guidebook - page caching

[jshook]

Presently, for any page loaded to a client, all of the markdown files have to be loaded and parsed. This is very inefficient and makes the user experience worse with larger sets of documentation. The markdown services already provide a cache version which can be used to avoid reloading for hot-load scenarios.

This enhancement is to read and cache the markdown on the client, and, when a reload is requested, to re-read the cache version from the service and avoid doing a full reload and parse when possible.