add a few missing dimensions

This makes getSIDouble*() work on PORO and PVTW.
add dimensions for the PVDG table
add dimensions to the SGOF keyword
add dimensions to the PVTO keyword
Merge pull request #79 from andlaus/more_dimensions

add a few missing dimensions
Table collection keywords PVTO and PVTG now have individual items: settings.
Merge remote-tracking branch 'upstream/master' into tablecollection-with-items
make the getSIDouble*() methods const

the fact that data is lazily converted to SI units should not be
relevant for the caller. This requires to decorate the array for SI
units in the DoubleItem as mutable, though...
add a few 'explicit' statements

this allows to constructs like

ParserIntItem("NRPVT");

which IMHO is more readable than the previous way, i.e.,

ParserIntItem(std::string("NRPVT"));
Merge pull request #81 from andlaus/decorations

add some method decorations
Merge pull request #80 from joakim-hove/tablecollection-with-items

Tablecollection with items
units: fix typo

Raito -> Ratio
Units: fix thinko

milli means division by 1000 not multiplication...

this makes SPE1 converge nicely with opm-parser in autodiff!
Merge pull request #82 from andlaus/unit_system_fixes

Unit system fixes
fix more (hopefully all) conversion factors

also, correct the dimension of the Rv item of the PVDG keyword which
is 1/Rs. Finally, the conversion factor for stock tank barrels to m^3
was off by a factor of 1000. (I suppose that liters instead of m^3
were assumed to be the SI unit in this case.)
Merge pull request #83 from andlaus/fix_more_conversion_factors

fix more (hopefully all) conversion factors