Use path references from the root of the project

It becomes harder to move the directory around, but it now works equally
well with both recursive and non-recursive build systems.
Move test programs out of the source tree
Import cmake/ from commit 5f82198c in opm-core
Remove opm-core specific customizations
Search and replace opm-core with dune-cornerpoint

Add dependencies that are specific for this library as well as doing
the textual replacement in the configuration file.
Ignore output from CMake build
Remove remnants of the Autotools build system
Fixed the testing programs so that they compile.

They should be moved to opm-core, though, and the classes
[Nonu|U]niformTableLinear classes removed from opm/porsol/common
(they are already in opm/core/utility.
List files that are needed to build the library

This list will be picked up by the modules at a later commit.
Specify source files explicitly rather than with glob
Allow uppercase alternatives for package location vars
Fix bug with whitespace at end of env.var.
Don't add anything if no precompiled header is specified
Only regenerate config var file if actually changed
Remove make execution wrapper
Conditionally disable example if compiler is not C++11
Find OpenMP in a reusable way
Use OpenMP in this project

The source code have #pragma omp, so we should enable this from the
command line. (But why isn't it inherited from opm-core?)
Merge pull request #20 from rolk/020_cmakeupd

Update CMake scripts to commit 11bf7bf3 from opm-core
Update CMake scipts to commit e75d69ef from opm-core