Add "check for updates" functionality

[njhillson]

One drawback to desktop applications is that they can become out of date. It would be good for OVE electron to add functionality that enables the user to check for updates (and automate the updating process), alert the user that there are updates available (and point them to where they can get them), automatically update the software etc. Some implementation thereof would be good. If this functionality already exists, made it more apparent to the user that it is doing this on their behalf, e.g. under Help menu indicate that the version installed is up to date or not. Not trying to be prescriptive here of the solution, but just to make sure that this issue is considered and responded to in some form when possible.

[tnrich]

Plan:

• [ ] add a simple component to the ove-electron editor to check the current version against the latest released ove-electron version and display a warning if not fully up to date.