Reset cache automatically upon version change

[lloeki]

Pointer from Ian:

FYI, Mattermost version is apparently in the header of each request: https://github.com/mattermost/platform/blob/4f1dbb8ca9a6cce09c9a20e91e074feaadd755a8/model/client.go#L20 Here is where it is set: https://github.com/mattermost/platform/blob/master/api/context.go#L168

[LongLiveCHIEF]

Some of the things that need to be scraped change from version to version. The version in the header can be used to trigger a cache reset, but there still isn't a way to ensure correct functionality of the matterfront components, since end users could have any, version of mattermost connected, and even multiple different versions of mattermost connected.