Ert 697 load region defintion

This PR contains functionality to update en EclKW instance with the REGION content:

1. Class CreateRegion() will load build a region definition based on Faults and Polygons.
2. The REGION keyword will be updated with *whole* faultblocks, depending on whether the center of the faultblock is part inside the definition.

Functionality is sane and works; in particular very uncertain about the name CreateRegion.
Is CustomRegion a reasonable name?