Removed cpos = ~cpos constructions for closing a well; using well_controls_shut_well explicitly instead.
Will check if a well is open before throwing for an invalid control.
Read keyword PLYSHEAR.
Merge pull request #514 from joakim-hove/wells-cpos-manipulation

Removed cpos = ~cpos constructions for closing a well
Merge pull request #520 from qilicun/plyshear

Read keyword PLYSHEAR.