Fix gmx solvate topology updating

Fix gmx solvate topology updating

The topology update of gmx solvate was hardcoded to SOL molecules
(and some of the reported quantities also registered HOH and WAT).

Changed to allow updates based on any solvent molecule information.

Also, now allows for updates with multiple solvent molecule types
in the input solvent configuration

Added test case for topology update with multiple solvents

fixes #1929

Change-Id: If506e0f509c8a25cb615fb8d3f15b4dfdb239afa