Sparse-Uint: bug fix & added performance tests

This PR does:
- fix a bug in getindex_general.  Indexing with a disordered array lead to a no-methods error:
  `ERROR: no method SparseMatrixCSC{Tv,Ti<:Integer}(Int64, Int64, Array{Int64,1}, Array{Uint32,1}, Array{Float64,1})`  Test added.
- temprary fix for #7197 in `test/sparse.jl`
- added performance tests for Sparse-uint matrices