Remove trailing empty element on dependency list

An extra semi-colon had snuck in here which caused the project to be
dependent on a module called "", which of course failed further down
the line.

This error was previously undetected because we didn't have anything
that depended on opm-upscaling.
Detect empty elements in dependency list

These errors are usually an extra trailing semi-colon, which is easy
to put in there for symmetry with the other lines. Give a warning on
this but proceed with the build as usual afterwards.
Allow user to override our non-standard defaults

CMake loads option defaults from the platform file and then usually
proceeds to write these to the cache, so it is not possible to see
if an option was specified by the user, or was the default.

By setting CMAKE_NOT_USING_CONFIG_FLAGS, we regain control over the
options and can then set this to what we think is suitable, provided
that the user hasn't specified something for us.
Allow whole program optimization to be switched off
Minor refactoring to make code more readable
Report target architecture compiling for
Build release library by default

If you just download the source, compile and install, you get the
release library. Users who want to develop the code, must do setup
in their environment.
Merge pull request #28 from rolk/028_cmake

CMake rollup