add WELTARG keyword

this one is used deep inside opm-porsol and features a nasty context
dependent parameter...
Add more warnings to CMAKE_CXX_FLAGS.
Added missing dim argument in scatterDim function.
The ability to only specify top layer applies DX and DY as well. Fixed
resize() usage.
Added methods to export the ZCORN, COORD and ACTNUM keywords from the EclipseGrid.
Added functionality to export MAPAXES data.
Merge pull request #189 from joakim-hove/eclipsegrid-export

Eclipsegrid export
Merge pull request #188 from joakim-hove/EclipseGrid-fixes

Eclipse grid fixes
Merge pull request #183 from atgeirr/more-warnings

Add more warnings to CMAKE_CXX_FLAGS.
Merge pull request #180 from andlaus/add_weltarg

add WELTARG keyword
Removed contextDependent dimension
Removed extra ,