fix JSON of the PVTO keyword

the magic word is "num_tables" and not "size". with the latter it only
parses the first record of the keyword. Stupid me!
add dimensions to PVTG
add class for simple tables

This is intended for keywords like SWOF which currently is a big
vector of doubles but one needs to use the data in a column oriented
way.

This class is intended to be used like this:

Opm::DeckKeywordConstPtr swofKeyword = newParserDeck->getKeyword("SWOF");
Opm::SimpleTable swofTable(swofKeyword,
                           /*columns=*/std::vector<std::string>{"SW", "KRW", "KROW", "PCOW"},
                           /*recordIdx=*/table_num);
const std::vector<double>& sw = swofTable.getColumn(0);
// ...

what might be useful is to move the column names into the JSON
description of the keywords, but I could not find a way to go back to
the parser from the deck/keyword. maybe this is not even desireable as
decks might also be created by other means...

Also, a multi-record variant of the class is available. That one is
intended for keywords like PVTO where the first few items of each
record form a table (in the case of PVTO: Rs, pressure, Bo, and
viscosity for staturated oil) and the next entries constitute another
table (in the case of PVTO: pressure, Bo and viscosity for
undersaturated oil with the same RS factor as the first entry).

The second kind of tables can be constructed using the item-based
variant of SimpleTable.
add support for full-fledged tables
add utility classes for some common keywords

the idea is to create a lightweight wrapper objects around
DeckKeywords which allow more convenient and more readable access to
the data. E.g. instead of

  std::vector outerColumnNames{"RV", "P", "BG", "MUG"};
  std::vector innerColumnNames{"P", "BG", "MUG"};
  Opm::FullTable pvtgTable(deck->getKeyword("PVTG"),
                           outerColumnNames, innerColumnNames);
  pvtgTable->getOuterTable()->getColumn(1);

one now better uses

  Opm::PvtgTable pvtgTable(deck->getKeyword("PVTG"));
  pvtgTable->getOuterTable()->getPressureColumn();

the idea for the other keywords is similar.
remove the emacs and vim modelines

as it was decided that having editor-specific stuff in files is not
wanted in OPM. for emacs, a .dir-locals.el file is added to the
module's root directory which should have the same effect.
move the SimpleMultiRecordTable class into its own files.
also constify the getSIDoubleData() method in DeckKeyword

in the item and in the record it already was marked as const, the
DeckKeyword class was forgotten during that excercise.
Units: add 'Timestep' dimension

the motivation for this is the 'TSTEP' eclipse keyword.

the reason why this dimension is not simply called 'Time' is that in
eclipse, different keywords might use different units, e.g. one
keyword could use seconds, another could use years while a third uses
days. As an added bonus, the used time units may be different for
different scales but identical in others (e.g., for one keyword times
might be specified in 'days' for the metric as well as for the
labscale, but in 'days' and 'hours' for another second keyword.)
add utility class for the 'TSTEP' keyword
add wrapper class for the START keyword
add unit test for SGOF
add a wrapper for records of the WELSPECS keyword
fix more of the annoying sign comparison warnings

hopefully all of them.
add a wrapper class for the "SPECGRID" keyword
add wrapper class for "WCONINJ"
add wrapper classes for more eclipse keywords

these are convenient to convert everything required to rip out the old
parser of sim_fibo_ad. the concrete keywords are:

 - COMPDAT
 - EQUIL
 - GCONINJE
 - GCONPROD
 - GRUPTREE
 - WCONINJE
 - WCONINJ
 - WCONPROD
 - WELOPEN
 - WELSPECS
 - WGRUPCON

in the medium term it would be nice if these wrapper classes could be
automatically generated from the JSON keyword descriptions.
add additional dimensions for the keywords required to convert autodiff's sim_fibo_ad
some additional dimensions for keywords used by the Norne case
implement multi-region full tables

detecting empty records is still pretty hacky: When calculating the
number of flat items, we stop at the first item for which the default
was applied.

Also, this patch corrects the names of the columes used by the PVTG
keyword. (the first column is pressure, then comes Rv.)