Refactor WellProductionProperties manipulation code

This commit splits the creation of WellProductionProperties objects,
and especially the ad-hoc helper functions historyProperties()
and predictionProperties() out to a separate module,
WellProductionProperties.[hc]pp.  Creating the properties object
from a DeckRecordConstPtr is deferred to two named constructors,

    WellProductionProperties::history() and
    WellProductionProperties::prediction()

that, respectively, assume the roles of historyProperties() and
predictionProperties().  Reimplement handleWCONProducer() in terms
of these named constructors and remove the producerProperties()
helper whose task, inspecting the status and retrieving/setting the
CMODE if not SHUT, can be assumed by handleWCONProducer().

Add a simple test module, WellPropertiesTest.cpp, to enforce the
rather peculiar semantics of the WCONHIST keyword.  Control modes
{O,W,G}RAT, LRAT, and RESV are *always* (unconditionally) supported
in WCONHIST but there is no control mode switching.  The latter is
deferred to client code, depending on the '.predictionMode' flag.

Suggested by: [at] joakim-hove

opm/parser/eclipse/EclipseState/Schedule/tests/WellTests.cpp

@@ -32,6 +32,7 @@
 #include <opm/parser/eclipse/EclipseState/Schedule/ScheduleEnums.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/Well.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/TimeMap.hpp>
+#include <opm/parser/eclipse/EclipseState/Schedule/WellProductionProperties.hpp>
 
 static Opm::TimeMapPtr createXDaysTimeMap(size_t numDays) {
     boost::gregorian::date startDate( 2010 , boost::gregorian::Jan , 1);