Include config.h in cpp file.
Make all codes use the same linear interpolation routines.
Finished unification of linear interpolation.

The functions of linInt.hpp are now used everywhere, but:
 - linInt.hpp -> linearInterpolation.hpp (better name)
 - linearInterpolationExtrap() -> linearInterpolation() (extrapolate by default)
Remove linInt.hpp from header list.
Simplified class NonuniformTableLinear.

Removed the policy control for what to do beyond the domain.
Old behaviour was constant extrapolation, current behaviour
is linear extrapolation. The possibility to choose was never
needed and has beem removed.
Added test for class NonuniformTableLinear.

Formerly lived in opm-porsol.
Added test for class UniformTableLinear.

Moved from opm-porsol.
Whitespace cleanup.
Merge pull request #219 from atgeirr/cleanup-interpolation

Cleanup of linear interpolation utility