Implement system solver class

[pelesh]

The system solver is supposed to be a high-level API for ReSolve. This class should also manage options settings.

This PR delivers main functionality for the SystemSolver class. It includes:

• Basic methods for parameter settings.
• Adjustments to linear solver classes interfaces.
• Removes loophole in functionality tests that could lead to false positives.
• Adds functionality tests and usage examples for SystemSolver class.
• Closes: KLU Direct Solver rcond functionality needed #95.

[kswirydo]

will compile and run next.

[kswirydo]

When I run the system.exe example on ascent, I am getting
./examples/system.exe ../tests/functionality/ terminate called after throwing an instance of 'std::logic_error' what(): basic_string::_M_construct null not valid Aborted (core dumped)
same with system_cuda.exe

[pelesh]

@maksud, please check if the issue #95 is fixed in this branch.

[kswirydo]

So both syssolver test with cuda and klu_glu test gives this (for the first matrix) which is obviously wrong
||b-Ax||_2 : 2.88790648555419e-12 (residual norm)
||b-Ax||_2 (CPU) : 2.483452223531182e-12 (residual norm)
||b-Ax||_2/||b||_2 : 1.465835083417962e-18 (scaled residual norm)
||x-x_true||_2 : 5.382658656691419e-12 (solution error)
||x-x_true||_2/||x_true||_2 : 7.898611154542518e-14 (scaled solution error)
||b-Ax_exact||_2 : 1970144.198500361 (control; residual norm with exact solution)
(I fixed this, see the newest commit)
All other tested exampleswork.