Grid properties: get rid of the dimension string for integer properties

this uses a small amount of template magic, to automatically change
the API of the GridProperty class depending on wheter it is
instantiated for double or for int.
Merge pull request #230 from andlaus/remove_dimensionString_from_integer_grid_properties

Grid properties: get rid of the dimension string for integer properties
add some missing transmissibility multiplier keywords

and add a dimension to MULTZ
property operators: add quite a few additional keywords

These are all keywords which are used by the Norne deck within some
property modifiers plus all variants of these. (sans the variants for
radial grids which are completely pointless IMO.) The chances that
keywords which have not been added yet can also be used are very close
to 100%, though.

Note that the default values for these keywords are currently
incorrect as the Eclipse RM states that the values must be looked up
in their corresponding table if the keyword is left unspecified (see
e.g. the documentation SWU). This probably means that we need to
implement "ghosty" keywords which magically appear if they have not
been explicitly specified or maybe we should only provide them in
EclipseState to be able to do the context dependent table look-up
"vodoo"...
Merge pull request #232 from andlaus/modifiers_add_more_supported_keywords

Modifiers add more supported keywords