Move towards explicit `solve(B,X)` interface for `LinearSOE`

[claudioperez]

This will eliminate bugs like #127 and helps implement #131

Tests are implemented by simpsoba/benchmarks#3

Progress:

Class	formAp	getDeterminant	solve(b,x)
BandGenLinLapackSolver	⚠️	Y	#137
BandSPDLinLapackSolver	⚠️	❌	#137
DiagonalDirectSolver	Y	Y	Y
DistributedDiagonalSolver	❌	❌	❌
FullGenLinLapackSolver	Y ⚠️	Y	Y
SuperLU	❌	❌	#138
SymSparseLinSolver	❌	❌	Y
UmfpackGenLinSolver	❌	Y	Y
UmfpackSolver02	❌	Y	Y
ProfileSPDLinDirectSolver	Y	Y	Y
ProfileSPDLinSubstrSolver	Y	Y	Y
ProfileSPDLinDirectBlockSolver	Y	❌	Y
ProfileSPDLinDirectSkypackSolver	Y	❌	❌
SProfileSPDLinSolver	❌	Y	❌
ItpackLinSolver	❌	❌	❌
MumpsSolver	❌	❌	❌