Add julia lu factorization. Fix some promotion for linear systems and fix bidiagonal and triangular solvers for multiple right hand side. As consequence, change \ for bitarray to return Array{Float32} and introduce convert methods for sparse matrices without specifying integer type. Devectorize matrix norm.
Merge pull request #5381 from JuliaLang/anj/rational

Add julia lu factorization. Fix some promotion for linear systems and fix bidiagonal and triangular solvers for multiple right hand side.