Removing molecular events - merging successive reactions with the same enabler and GO MF term

[vanaukenk]

In Reactome, when two successive reactions share the same GO MF and the same enabler, they should be merged in the GO-CAM, with the Reactome reaction id of the second of the two reactions retained.

This may not account for everything (e.g. product dissociation), but should get many of the relevant cases.