Utility functions to check if deck has sections.
Added grid method getCartesianSize()
Added isDataKeyword() property to deckKeyword.
Added GridProperty class.
Added grid properties container.
Added GridProrpties to EclipseState.
Embedded unit system from opm-core to ensure proper conversion factors.
Make conversion factors more readable.

The using directives will put a lot into the Field and Metric
namespaces, but it should not be problematic.
Merge pull request #213 from atgeirr/conversion-factors

Conversion factors
Merge pull request #207 from joakim-hove/gridproperties

Gridproperties
fixed: don't mix member names and function parameters
fixed: linking due to several specializations being generated
Merge pull request #214 from akva2/fix_warning

fixed: don't mix member names and function parameters
Merge pull request #215 from akva2/fix_linking

fixed: linking due to several specializations being generated