ENH: generalise masterCoarsest restart (GAMG)

.../GAMGAgglomerations/GAMGAgglomeration/GAMGAgglomeration.C

.../GAMGAgglomerations/GAMGAgglomeration/GAMGAgglomeration.H

...aicPairGAMGAgglomeration/algebraicPairGAMGAgglomeration.C

...AMGAgglomerations/dummyAgglomeration/dummyAgglomeration.C

...AMGAgglomerations/dummyAgglomeration/dummyAgglomeration.H

...gglomerations/pairGAMGAgglomeration/pairGAMGAgglomerate.C

...lomerations/pairGAMGAgglomeration/pairGAMGAgglomeration.H

...lomerations/GAMGProcAgglomeration/GAMGProcAgglomeration.C

...MGProcAgglomeration/masterCoarsestGAMGProcAgglomeration.C

...MGProcAgglomeration/masterCoarsestGAMGProcAgglomeration.H

...ices/lduMatrix/solvers/GAMG/GAMGSolverAgglomerateMatrix.C

...AreaPairGAMGAgglomeration/faceAreaPairGAMGAgglomeration.C

...GAMGAgglomeration/assemblyFaceAreaPairGAMGAgglomeration.C

...ods/MGridGenGamgAgglomeration/MGridGenGAMGAgglomeration.C

tutorials/compressible/rhoSimpleFoam/squareBendLiq/Allrun