Edited Task: Review behavior of REngine.Initialize [121]

I think I need to keep the Initialize API in some use cases, in addition to GetInstance. Do I really? the inconvenient is that it currently silently ignores calls more than once. This may create issues for users unaware (or who do not see the XML docco from the IDE).

Reconsider, in light of https://github.com/BlueMountainCapital/FSharpRProvider/pull/107