"Update available check" should wait for release vs release branch

[ghormann]

Today the service that notifies of new releases just looks at ranches. (see https://github.com/FalconChristmas/fpp-stats-server/blob/master/server/lib/github.js) We should investigate modifying this to wait for full releases that have artifacts.

[ghormann]

I've made some changes to the backend server to allow information on "releases" to be available. See https://github.com/FalconChristmas/fpp-stats-server/blob/master/server/docs/API.md#7-fpp-git-commits

I still need to find some time to update the FPP side to take advantage of the new "releases" section of the API.