Fix/mesh partition
This MR fixes and issue with using the WeightPartition SolverInfo. When restructuring the Mesh partitioning/input strategy which required moving MeshPartition.cpp from LibUtilities to SpatialDomains we were incorrectly filling in the structure m_expansions with all the information from the composite list rather than just those mentioned in the EXPANSION section. This then was causing an out of bounds request in the WeightPartitions routine.