Add SparseVector.NonZerosCount property
Remove zlib NuGet packages.config project reference #76
Merge pull request #79 from tibel/sparsevector-nonzeroscount

Add SparseVector.NonZerosCount property
LA: Perf, drop some range checks
LA: Matrix storage: clarify checked vs unchecked
LA: Vector storage: clarify checked vs unchecked
LA: Delegate Matrix Row/Column methods to storage classes
LA: Make storage-arg Matrix/Vector ctors public
Delegate Matrix To(Row/Column)Array to storage classes
Cosmetics: Matrix class structure (no code changes)
Control: choose default linear algebra provider by env var

Setting the variable MathNetNumericsLAProvider=MKL
will now make Control default to the MKL provider.

If non is set or setting it fails, it will fall back
to the managed provider as before.
Control: disable envvar default provider in portable build
Native Pull: Updated provider and bug fixes

mathnet-numerics-native a6e5c948049bda46cb3b5625fa41accebaa4bdb3:
1. Updated the native provider to MKL V11 update 2, which fixes the lange bug.
2. Re-enabled native matrix norms.
3. Fixed complex Frobenius norm bug in managed code (we weren't taking the conjugative transpose).
4. Fixed the return type on the double matix norm in the managed side of the native provider.