Refactor qmake SUBDIRS structure

The big swift.pro is refactored by the correct usage of SUBDIRS
template. The following additional changes are made:
- Removed '_' from all targets and folder names
- Aligned parent folder and target name

refs #461

src/plugins/simulator/fsxconfig/simulatorfsxconfig.json

@@ -0,0 +1,3 @@
+{
+    "identifier" : "org.swift-project.plugins.simulator.fsx.config"
+}