Add test that different linear solve paths are equivalent

solve(a == L, out) should be the same as
solve(assemble(a), out, assemble(L))
Merge pull request #49 from firedrakeproject/solver-parameters

Fix the setting of solver parameters on FooSolver objects.
Previously, the solver options were only set in the constructor.  Hence
the following did not work:

    solver = FooSolver(...)
    solver.parameters.update(...)
    solver.solve()              # updated parameters ignored

Fix this by updating the solver options at the beginning of every solve
call.  As a side effect, the linear solver now actually only does a
single newton iteration!  Furthermore, fix up the parameters in
_la_solve to match those in the variational solve call.
Misc docstring fixes in core_types
Return None for op2.Halo if sends and receives are empty
Use make_dat to create Dat on a FunctionSpace
Only flatten Args on VectorFunctionSpaces
Sphinx config: use docstrings of class and __init__ method
Docstring fixes for solving
Merge pull request #50 from firedrakeproject/misc

* Only flatten Args on VectorFunctionSpaces
* Use make_dat to create Dat on a FunctionSpace
* Return None for op2.Halo if sends and receives are empty
* Docstring fixes for core_types and solving
Introduce a feed of recent commits on the front page of the website.
docs template: Purge leftovers from dolfin-adjoint
docs template: load current jQuery from CDN
docs template: add Google Analytics
Fix docstring syntax.

Fix a whole load of mystyped directives, missing blank lines and missing indentation.
CSS rule to disable the Travis logo
Add acknowledgement of our funders.
Add a funding link to the navigation bar.
Add Michael Lange, and consequently, ESE, to the team.
Allow running test suite in parallel through Makefile

make test THREADS=8 now runs the testsuite using 8 processes,
significantly speeding things up.
Merge pull request #55 from firedrakeproject/parallel-test

Now you can say make THREADS=N test to run the test suite in
parallel (requires pytest-xdist plugin).