REQS-666/PLAT-6851 Stage 6 (final stage)

This is the sixth and final stage of [REQS-666](https://opengamma.atlassian.net/browse/REQS-666), ticket [PLAT-6851](https://opengamma.atlassian.net/browse/PLAT-6851), which is to remove the deprecated method `toDerivative(ZonedDateTime date, String... yieldCurveNames)` from the class [`InstrumentDefinition`](https://github.com/OpenGamma/OG-Platform/blob/develop/projects/OG-Analytics/src/main/java/com/opengamma/analytics/financial/instrument/InstrumentDefinition.java#L26).

For context please see Stage 1 in PR https://github.com/OpenGamma/OG-Platform/pull/262. The methodology and rulings outlined there are in use in this PR.
This PR is the natural continuation of Stage 5 in PR https://github.com/OpenGamma/OG-Platform/pull/266, Stage 4 in PR https://github.com/OpenGamma/OG-Platform/pull/265, Stage 3 in PR https://github.com/OpenGamma/OG-Platform/pull/264 and Stage 2 in PR https://github.com/OpenGamma/OG-Platform/pull/263.

Note: this may need some patching on the engine side in the future.