Detect MinKNOW version and warn.

[mattloose]

As of MinKNOW 5.9 there is a change in how unblocks will be handled. To address this we should implement:

### Tasks
- [x] Detect MinKNOW version on launch and check compatibility
- [x] Proceed as usual if readfish and minknow are compatible.
- [x] If not compatible, alert user and recommend alternate versions of readfish.