UDQ: fix bug with parsing of expressions like A - B - C - D

- In the case of several tokens separated with +/- the final tree is assembled
   from left, was previously from the right. This fixes evaluation bug with
   expressions like A - B - C which were eventually evaluated as A - (B - C).

 - Improved handling of different types; both transiton from scalar to sets of
   wells and groups, and also groups in general. In particular you can now
   assign to a group variable:

        DEFINE GUXXX  WOPR * 0.25

 - Actually hook up the evaluation of group variables from the Summary code.

opm/parser/eclipse/EclipseState/Schedule/UDQ/UDQEnums.hpp

@@ -59,14 +59,14 @@ namespace Opm {
 enum class UDQVarType {
     NONE = 0,
     SCALAR = 1,
-    WELL_VAR = 2,
-    CONNECTION_VAR= 3,
-    FIELD_VAR = 4,
-    GROUP_VAR = 5,
-    REGION_VAR = 6,
-    SEGMENT_VAR = 7,
-    AQUIFER_VAR = 8,
-    BLOCK_VAR = 9
+    CONNECTION_VAR = 2,
+    FIELD_VAR = 3,
+    REGION_VAR = 4,
+    SEGMENT_VAR = 5,
+    AQUIFER_VAR = 6,
+    BLOCK_VAR = 7,
+    WELL_VAR = 8,
+    GROUP_VAR = 9
 };
 
 
@@ -165,8 +165,10 @@ enum class UDAKeyword {
 
 namespace UDQ {
 
+    UDQVarType targetType(const std::string& keyword, const std::vector<std::string>& selector);
     UDQVarType targetType(const std::string& keyword);
     UDQVarType varType(const std::string& keyword);
+    UDQVarType coerce(UDQVarType t1, UDQVarType t2);
     UDQAction actionType(const std::string& action_string);
     UDQTokenType funcType(const std::string& func_name);
     bool binaryFunc(UDQTokenType token_type);
@@ -177,7 +179,6 @@ namespace UDQ {
     std::string typeName(UDQVarType var_type);
     UDAKeyword keyword(UDAControl control);
     int uadCode(UDAControl control);
-
 }
 }