Res2df

Defer loading of treelib until needed.
* No longer necessary to have treelib installed in order to import ecl2df, only when this tree-functionality in gruptree is requested.

Feature release:
* New pillar module, for computations on cornerpoint pillars volumes, statistics, and fluid contact determination over time.
* ecl2csv subparser 'smry' renamed to 'summary'
* ecl2csv summary supports specifying start and end dates.
* compdat module can merge zone-names and INIT-vectors
* Docs upgraded

Changes:
* Breaking API change: Submodules under ecl2df has "2df" removed from their name. Backwards compatibility only for satfunc2df and compdat2df.
* NNC fix, previous version gave erroneous data.
* NNC output can be limited to only vertical pillars (to analyze pinches etc.)
* summary output can include data from parameters.txt
* Stacking option for RST data (by date)
* Add a zone map option, so that K indices can be mapped to a zone string.
* Add function to build a dataframe of cell transmissibility pairs, similar to NNC (no command line tool yet)

New command line frontend `ecl2csv` with subcommands. All individual commands are now deprecated, and will be removed in a future version.

satfunc2df and equil2df can infer the number of saturation regions or equilibrium regions when TABDIMS/EQLDIMS are not present.

Changes:
* Support GRUPNET
* WELSEGS fixed.
* Support TSTEP
* deck2df() as standard module function for DATA-file parsers.
* More logging.
* Verbose option to scripts