ProjectExplorer: Add convenience function BuildStepList::appendStep().

In most cases, there is no value in writing out the index explicitly,
and it is downright annoying when adding steps conditionally.

Change-Id: I2a3947d3dbc11364046c0917c661497d0720725a
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/projectexplorer/buildsteplist.h

@@ -58,6 +58,7 @@ public:
     bool contains(const Core::Id id) const;
 
     void insertStep(int position, BuildStep *step);
+    void appendStep(BuildStep *step) { insertStep(count(), step); }
     bool removeStep(int position);
     void moveStepUp(int position);
     BuildStep *at(int position);