Swap clock-clause and solverMethod, and rename

This is still being discussed, but the original proposal was not popular at all.

RationaleMCP/0031/differences.md

@@ -1272,8 +1272,8 @@ partition /* Beginning of base-partition */
     'baseVar' = sample('x');
 
   subpartition
+    discretization "ImplicitEuler";
     Clock _subClock0 = subSample('baseClock', 2); /* Automatically generated clock name. */
-    solverMethod "ImplicitEuler";
   equation
     der('cVar1') = noClock('baseVar');
 

RationaleMCP/0031/grammar.md

@@ -183,8 +183,8 @@ end _F;
 
 > _sub-partition_ →\
 >   **subpartition** _comment_\
+>   ( **discretization** _STRING_ **;** )?\
 >   _clock-clause_ **;**\
->   ( **solverMethod** _STRING_ **;** )?\
 >   ( **equation** ( _equation_ **;** )* \
 >   | **algorithm** ( _statement_ **;** )* \
 >   )*