Updates to well control mode reported in IWEL

With this commit the IWEL[ActWCtrl] is assigned a value independently of the
wells OPEN / SHUT status.

With this PR the index enum value Status is used instead of the previously used
item11. Also numerical constants are introduced for eclipse status values for
Shut, Stop, Open and Auto.

tests/SPE1CASE1.DATA

@@ -412,6 +412,7 @@ COMPDAT
 WCONPROD
 -- Item #:1	2      3     4	   5  9
 	'PROD' 'OPEN' 'ORAT' 20000 4* 1000 /
+	'RFT'  'SHUT' 'ORAT' 20000 4* 1000 /
 /
 -- It is stated in Odeh's paper that the maximum oil prod. rate
 -- is 20 000stb per day which explains the choice of value in item 4.