[DEV] added an option to control MKL Pardiso matrix type, in the hopes it lowers memory requirements for diffusion-only problems (which in FEM are structurally symmetric, oisitive definite)
[DEV] added same previous commit improvement to standalone-pardiso
[DEV] defined type-specific matrix type option
[DEV] some more options controling the solving step of stand-alone pardiso (hopefully allowing the use of the iterative solver).
Merge pull request #32 from pmaciel/pardiso

[DEV] Pardiso options on matrix type (MKL & stand-alone) and access to iterative solver (stand-alone).