Add spdiag() prototype to silence GCC 4.6 warning.

GCC's flag -Wmissing-declarations requires that a valid prototype
exist for non-template (global) functions prior to the corresponding
function definition.
Merge remote-tracking branch 'atgeirr/master'
Merge upstream changes.
Import CMake support from OPM-Core
This is OPM-Autodiff 0.1

We don't depend on any Dune modules.
First partitioning into source/examples/tests

Reorganisations are likely.
Move MRST example closer to actual example
Complete import of CMake support from OPM-Core
Adopt imported build system to OPM-Autodiff specifics

Updated include statements &c to follow.
Fix inverted set of automated test cases.
Adapt to CMake-based build system.

Specifically,

  - #include <config.h> where appropriate (all .cpp files)
  - Adjust include statements to account for sub-directory locations
    of .hpp files.
Merge remote-tracking branch 'atgeirr/master'
New sentence -> capital letter.
New sentence -> capital first letter.
Reduce tolerance, add alternative code path.

The alternative code path attempts to deal with floating point cancellation
issues, which may not turn out to be a problem in the end (for real cases).
Merge remote-tracking branch 'bska/master'