Revision 6104

Factored out and templetized preconditioner,solver and direct solver creation.
The SystemMatrix constructor now takes an optional arg 'isComplex'.
Some complex operations are commented out as we need the complex getSampleData*
methods from trunk for them to work.

It looks like we have to modify the Abstract class in escript eventually as
there is a single method that takes a `double` argument (nullifyRowsAndCols).