Integrate target support

* Ease cross device development by introducing 'targets' which
   group build- and runsettings that are valid for this one target

 Most of the kudos for the code review go to dt. Con, thorbjorn,
 ckandler and others did also review parts of this patch.

Reviewed-by: dt

src/plugins/qmlprojectmanager/qmlprojectconstants.h

@@ -38,7 +38,6 @@ const char *const LANG_QML           = "QML";
 const char *const QMLMIMETYPE        = "application/x-qmlproject";
 
 const char *const QMLRUNCONFIGURATION = "QmlProject.QmlLocalApplicationRunConfiguration";
-const char *const MAKESTEP            = "QmlProject.QmlMakeStep";
 
 // contexts
 const char *const C_FILESEDITOR      = ".files Editor";