Changes

Removed the IDAS solver (#1515).
 (commit: 499f88e)

Some minor cleaning up.
 (commit: 59fbd43)

Updated the documentation to remove references to IDA(S) (#1515).
 (commit: ae162f0)

Documentation: updated our KINSOL solver page (#1515).
 (commit: 486fa00)

Documentation: slight updates related to DAE models (#1515).
 (commit: 71ba6c5)

Solver interface: removed the VoiSolver and DaeSolver classes (#1515).
The contents of the VoiSolver class was merged into the OdeSolver class.
 (commit: e580447)

Solver interface: removed the DAE type of solver (#1515).
 (commit: 8b4beee)

CellML support: got rid of all the DAE-related code (#1515).
 (commit: cd68485)

CellML support: don't keep track of the type of model (#1515).
Indeed, if it is a DAE model, it will have some NLA equations to solve.
 (commit: 0cb02d6)

Solver interface: added a reinitialize() method (#1515).
Makes things cleaner for CVODES when we need to reinitialise it (when 
solving a DAE model; see SimulationWorker::started()).
 (commit: 716f191)

Slight update to our downloads page (#1515).
 (commit: d531784)