OpenFOAM matrix extraction

This contains 4 parts: 

 * MatrixExtractingSolver - an OF solver that writes the linear system
   to a file - works in parallel.
   
 * reconstructSystem - an OF utility to reassemble the output of a
   parallel run into a single file (a la reconstructPar).

 * convertSystem - an OF utility to read a (possiby reconstructed)
   .system file and write out simple text format files (.vec and .coo)
   which represent the vector and COO format matrix, respectively.

 * FoamMatrix.py - simple python module to read the above for further
   processing (required numpy and scipy).