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.