[0.9.1] Research resets after switching

[Rwn]

If you start reseaching a technology, then switch to another research before completion, the progress on the first is lost (e.g. if you start researching it again later).

This might not be a bug, but a feature (through a bit counter-intuitive).

[slpwnd]

This is intended behavior. The player needs to think twice before cancelling existing research.