Invalidate Repo and Permission Cache

[bradrydzewski]

The list of user repositories and the permissions to those repositories are cached in a simple LRU cache without expiration (due to lack of time on my part to focus on caching). We need a TTL to avoid rendering stale data in the user interface, otherwise this can result in the following behavior:

1. search results / auto-complete do not include recently added repositories
2. dashboard does not include recently added repositories
3. recently elevated repository permissions (ie changing write -> admin) are not considered

There will still be situations where our cache is stale, but we can handle this well enough in the user interface. For example, when I search for a repository that isn't in our cache (perhaps was recently created) we can show a message that says something like this:

{repo_name} is unknown or does not exist. Click here to visit this repository page and activate.

We can also provide a button to manually flush the cache in order to force a refresh.

[bradrydzewski]

implemented a 24 hour cache and informational messages in the UI in case the cache is stale

[bradrydzewski]

changed to 15 minute cache a few weeks ago until we have a way to force-refresh from the UI

[bradrydzewski]

This fix landed for the upcoming 0.5 release by providing a button to re-sync your account. See screenshot