[Opm] Refactoring of EclipseState and Schedule

[Atgeirr Rasmussen]

Dear OPM community,

In order to better support using Flow as a component, and gain some "scriptability", we propose to refactor the relationship between the EclipseState and Schedule classes of opm-parser. Currently the EclipseState owns the Schedule. We propose to make the Schedule class independent in the sense that it will not be owned by an EclipseState instance, although constructing it would still require an EclipseState object. This means that some methods in downstream modules will gain an additional (Schedule) parameter, for some methods a Schedule parameter will replace an existing EclipseState parameter.

The end result is that it will be possible for third party developers to easily create programs that manipulate the schedule before passing it to the simulator component, such as for example NTNU's FieldOpt program.

Joakim and Atgeirr