Begin port of modeler algorithm to c++

Author: nyalldawson

python/core/core.sip

@@ -288,6 +288,7 @@
 %Include processing/qgsprocessingalgrunnertask.sip
 %Include processing/qgsprocessingcontext.sip
 %Include processing/qgsprocessingfeedback.sip
+%Include processing/qgsprocessingmodelalgorithm.sip
 %Include processing/qgsprocessingoutputs.sip
 %Include processing/qgsprocessingparameters.sip
 %Include processing/qgsprocessingprovider.sip

python/core/processing/qgsprocessingalgorithm.sip

@@ -276,6 +276,12 @@ class QgsProcessingAlgorithm
  :rtype: bool
 %End
 
+    void removeParameter( const QString &name );
+%Docstring
+ Removes the parameter with matching ``name`` from the algorithm, and deletes any existing
+ definition.
+%End
+
     bool addOutput( QgsProcessingOutputDefinition *outputDefinition /Transfer/ );
 %Docstring
  Adds an output ``definition`` to the algorithm. Ownership of the definition is transferred to the algorithm.